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Oolong Tea & Weight Loss: Does It Help Burn Fat?

Oolong tea is a traditional Chinese tea that remains popular throughout south China and Southeast Asia wherein it is referred to as “qingcha” or dark green tea.  When translated from Chinese to English, the term “oolong tea” roughly means “black dragon tea.”  Similar to both green and black tea, oolong tea is a product created from the leaves, buds, and stems of the plant Camellia sinensis.

The processing of oolong tea involves withering of Camellia sinensis under strong sun whereby it partially oxidizes before withering, rolling, shaping, and firing.  Most oolong tea manufacturers utilize unique Camellia sinensis cultivars to ensure optimal oxidation percentages and fermentation.  The degree of oolong tea leaf oxidation can range from 8% to 85% and its flavor can vary significantly depending on the specific cultivation process.

Compared to green tea and black tea, oolong tea is partially fermented and oxidized, whereas green tea is non-fermented and minimally oxidized and black tea is fully fermented and fully oxidized.  Not only do many consumers enjoy the unique flavors of oolong tea varieties, some believe its consumption may help with weight loss.

Could drinking Oolong tea cause weight loss? (If so, how much weight?)

Yes – but there are caveats.  If an adequate dose (i.e. strength) of oolong tea is consumed per day – modest weight loss and fat loss might occur in a subset of consumers.  However, weight loss and fat loss will only occur if oolong tea consumers don’t compensate for the oolong-tea mediated increases in 24-hour energy expenditure and fat oxidation by increasing calorie intake.

Evidence to support the idea that oolong tea could induce weight loss in humans can be derived from 2 studies.  Results from a study by Rumpler et al. (2001) indicated that full-strength oolong tea (brewed from 15 grams – containing an estimated ~270 mg caffeine) increased 24-hour energy expenditure by an average of ~281 kJ/day in healthy, normative-weight adult men.

Males (Normal weight, adults): ~1 lb. within 2 weeks (This is an estimate based off of increased 24-hour energy expenditure resulting from oolong tea (15 g) consumption).

Overweight & obese: ~5.95 lbs. within 6 weeks (This is an average based off of a study involving overweight, obese, and severely-obese individuals who consumed oolong tea (8 g) on a daily basis for 6 weeks).

  • Males (obese/overweight): ~6.61 lbs. within 6 weeks
  • Females (obese/overweight): ~5.29 lbs. within 6 weeks

If the results of this study can be extrapolated to a larger population, it’s reasonable to speculate that [if maintenance calories are consumed], an increase in energy expenditure of 281 kJ/day would put the average oolong tea consumer in a calorie deficit to yield weight loss of ~1 lb. within 12 days (under 2 weeks); this is assuming the increase of ~281 kJ/day is maintained.

The study by Rumpler et al. also noted that full-strength oolong tea increased fat oxidation by around 12% – suggestive that the weight loss resulting from its consumption is probably body fat.  Another study by He et al. (2001) involving 52 overweight participants (BMI: 25-30); 44 obese participants (BMI: 30-35); and 6 severely-obese participants (BMI: 35+) – reported weight loss after daily oolong tea consumption (8 grams) over a 6-week duration.

Results from the study by He et al. indicated that 70% of severely-obese participants, 64% of obese participants, and 66% of overweight participants – lost over 2.2 lbs. (1 kg) in the 6-week trial – and a subset of individuals in the severely-obese group lost over 6.61 lbs. (3 kg).  Males (40) in this study lost an average of 6.61 lbs. and females in this study lost an average of 5.29 lbs.

Multiple non-human studies involving animal models also support the idea that oolong tea may induce weight loss or protect against weight gain.  Research by Heber et al. (2014) discovered that oolong tea polyphenols promoted weight loss and/or protect against obesity resulting from the consumption of a high-fat diet over a 20-week period.

Moreover, a 10-week study by Han et al. (1999) discovered that oolong tea exerted an anti-obesity effect (via induction of lipolysis) among mice fed a high-fat diet.  Although data derived from 2 human studies of oolong tea on body weight are of low quality, all preliminary evidence supports the idea that daily consumption of adequately-dosed oolong tea could promote modest weight loss or protect against obesity in adults (regardless of sex or preexisting BMI).

Note: The weight loss amounts listed above are estimates and/or averages based upon data from relatively low-quality studies.  Even if the data are accurate, it is important to realize that the amount of weight loss resulting from oolong tea consumption will be subject to individual variation.

Oolong tea, Weight Loss, & Fat Loss (Potential Mechanisms)

Preliminary evidence suggests that regular (i.e. daily) consumption of oolong tea at a sufficient dose may induce weight loss.  Assuming oolong tea consumption is capable of inducing weight loss [in a subset of the population], below are some hypothesized mechanisms by which it may reduce body weight and improve body composition (by reducing body fat).

The most likely mechanisms by which oolong tea induces weight loss include: promoting lipid utilization (with caffeine), suppressing fat tissue functions (with catechins), controlling lipid absorption from the intestine, and increasing 24-hour energy expenditure.  Other possible mechanisms of oolong tea-induced weight loss might include: increasing postprandial satiety, decreasing appetite, enhancing self-regulation, and bolstering energy (for physical activity).

It is important to emphasize that these mechanisms are hypothesized and not fully substantiated with strong scientific evidence in humans.  Nevertheless, if you’re losing weight with oolong tea and are wondering how the weight loss is occurring – the mechanisms below warrant consideration.

Adipogenesis inhibition:  Research by Yang et al. (2015) suggests that multiple catechins within oolong tea (e.g. ECG, EGCG, etc.) are capable of inhibiting adipogenesis or the proliferation of new fat cells.  Although some research suggests that inhibiting adipogenesis may be unfavorable for weight loss due to the fact that adipogenesis inhibition is associated with deleterious metabolic changes (in the literature), oolong tea has been shown to induce favorable metabolic changes.

Because favorable metabolic changes occur after ingesting oolong tea components (e.g. caffeine, polyphenols, etc.), deleterious metabolic changes associated with inhibition of adipogenesis after oolong tea consumption are unlikely to occur.  Considering that fat cell production may be inhibited with simultaneous metabolic enhancement (rather than metabolic detriment) following oolong tea ingestion – it’s fair to surmise that this mechanism could promote healthy weight loss (or prevent excessive fat gain).

Appetite suppression: It is thought that oolong tea may contain compounds that help reduce or suppress appetite.  If appetite is reduced from drinking oolong tea, it is reasonable to suspect that appetite reduction could affect calorie intake (i.e. energy consumption) such that an oolong tea drinker consumes fewer calories on days of oolong tea consumption – than days on which oolong tea is not consumed.

In the event that oolong tea-mediated appetite reduction is significant enough to reduce one’s calorie intake (relative to pre-oolong tea consumption), then weight loss should be expected.  Though polyphenols within oolong tea might interact with neurochemical and/or hormone production to suppress appetite, it’s also possible that the caffeine content alone could reduce appetite.

A literature review by Schubert et al. (2017) reported that caffeine ingested 0.5 to 4 hours before a meal may suppress acute energy intake.  Assuming acute appetite suppression result from oolong tea ingestion and leads to a reduction in daily calorie intake – then this could be a mechanism by which weight loss occurs.

Cognitive enhancement: It is widely documented that regular tea consumption is associated with lower risk of cognitive impairment and decline – this link has been substantiated by numerous large-scale literature reviews and meta-analyses.  Furthermore, many studies have reported cognitive enhancement following the consumption of green tea, a product derived from the same plant as oolong tea (Camellia sinensis).

Additionally, as a standalone agent, caffeine has been shown to enhance various domains of cognition including: alertness; task-switching; and memory.  Because oolong tea contains caffeine and is similar in composition to green tea, each of which are cognitive enhancers, it’s reasonable to expect that oolong tea also enhances cognition.

Among persons who derive cognitive enhancement from oolong tea intake, it’s possible that the cognitive enhancement could lead to weight loss.  If aspects of cognition such as self-regulation, planning, and critical thinking are enhanced, this might make it easier for some individuals to plan healthy meals, restrict calorie intake, and/or abstain from overeating.

Diuretic & gastric emptying effect: The caffeine within oolong tea may enhance diuresis and gastric emptying to promote weight loss via elimination of water stores and digested materials.  Although losing weight in the form of water and digested materials is not “fat loss,” it is still [technically] weight loss.

Among persons with a history of delayed gastric emptying (constipation) and/or excessive water retention (bloating), the combination of diuretic and gastric emptying effect may yield substantial weight loss (e.g. 5 lbs. to 15 lbs.) in a short duration.  If you experience rapid weight loss from oolong tea consumption, it’s likely that this rapid weight loss is attributable to a combination of diuretic and gastric emptying effects.

Energy increase: Oolong tea contains caffeine which is understood to antagonize adenosine receptors to bolster sympathetic tone and neurophysiologic arousal.  Among persons consuming sufficiently-dosed oolong tea, it’s likely that the caffeine content will counteract fatigue, increase energy levels, and bolster motivation.

As a result of the caffeine-mediated increases in energy and/or motivation, it may be easier to initiate physical exercise (i.e. workouts).  Research suggests that caffeine (up to 3 mg/kg) can enhance exercise performance in terms of intensity and endurance, making it easier for caffeinated individuals to burn more calories while exercising (than those who aren’t caffeinated).

Moreover, even if the caffeine content within oolong tea doesn’t increase your motivation to exercise or improve your exercise performance, it will probably still bolster non-exercise activity thermogenesis (NEAT) whereby you move more (e.g. walk, fidget, etc.) throughout the day and burn extra calories.  If you feel more energetic after drinking oolong tea and are exercising (more intensely or for a longer duration) or moving more than usual as a result, this could explain your weight loss.

Fat metabolism (lipolysis): Most research suggests that oolong tea promotes weight loss and improves body composition by increasing fat metabolism.  Some reports suggest that oolong tea may accelerate body fat metabolism by: activating lipoprotein lipase, enhancing noradrenaline-induced lipolysis, and increasing 24-hour energy expenditure.

Components of oolong tea that are believed to enhance fat metabolism include: caffeine and polyphenols (EGCG, EGC, ECG, GCG, CG, and EC).  For example, caffeine within oolong tea is understood to increase metabolic rate and increase fatty acid availability via fat cell lipolysis.

Additionally, catechins and EGCG have been shown to decrease triglyceride accumulation; EGCG and ECG appear to inhibit acetyl-CoA carboxylase (implicated in fatty acid biosynthesis); and EGCG is thought to potentially inhibit aspects of fat cell functioning.  Oolong tea has also been shown to inhibit the intestinal absorption of dietary fat principally via blocking pancreatic lipase.

Gut bacteria modulation: Among persons who are overweight and/or obese, populations of pathogenic gut bacteria are frequently elevated.  It is hypothesized that high concentrations of pathogenic gut bacteria (as are observed in states of dysbiosis) can increase appetite, induce inflammation, alter neurotransmitter/hormone production, increase fat storage, and increase oxidative stress – all of which could result in body fat and body weight gain.

Although restricting calories and losing weight generally improves gut bacteria composition, it’s fair to hypothesize that some individuals with elevated concentrations of pathogenic microbes (relative to probiotic microbes) may struggle losing weight as a direct result of gut flora composition.  One means by which oolong tea consumption may promote weight loss is through modulating concentrations of gut microbiota.

A study by Cheng et al. (2018) noted robust increases in microbe diversity following the administration of oolong tea polyphenols [over a 4-week duration] in mouse models of obesity; increases in Bacteroidetes and decreases in Firmicutes were observed.  A different by Sun et al. (2018) reported that oolong tea polyphenols appear to alter the human intestinal microbiome by upregulating beneficial bacteria, downregulating pathogenic bacteria, and generating short-chain fatty acids (SCFAs).

Authors of the aforementioned studies suggested that oolong tea polyphenol-mediated changes in microbiome composition resulting may improve general health.  Among persons attempting to lose weight, these compositional changes (resulting from oolong tea polyphenols) might: reduce appetite (and food cravings); decrease fat storage; reduce inflammation; etc. – to promote weight loss.

Hormonal modulation: Another potential means by which oolong tea may promote weight loss is by modulating hormone production.  Research by Hintzpeter et al. (2014) suggests that tea compounds may inhibit the formation of cortisol by interacting with the enzyme 11-beta-HSD1; (the most potent inhibitor is EGCG).

Because cortisol levels and cortisol responsiveness are commonly altered among individuals who are overweight and/or obese, it’s possible that cortisol modulation via EGCG (a component of oolong tea) could favorably modulate cortisol in ways that directly or indirectly enhance weight loss.  Research by Shimada et al. (2004) also shows that oolong tea increases concentrations of adiponectin; low levels of adiponectin are linked to obesity – and high levels are associated with weight loss.

Other hormones that may be affected by oolong tea components (e.g. caffeine, polyphenols, catechins) include: insulin, leptin, ghrelin, resistin, testosterone, and estrogen.  Substantial modulation to any of the aforementioned hormones could yield weight loss – or enhance deliberate weight loss efforts.

Inflammation & oxidative stress reduction: Oolong tea consumption may reduce systemic inflammation and oxidative stress to induce weight loss.  A study by Hisanaga et al. (2014) reported that oolong tea theasinensins (a specific group of polyphenols) reduce levels of proinflammatory mediators such as: inducible nitric oxide synthase (iNOS), nitric oxide (NO), interleukin-12 (IL-12), tumor necrosis factor alpha (TNF-α), and monocyte chemotactic protein-1 (MCP-1).

Another study by Mao et al. (2017) reported that tea polyphenols generally scavenge free radicals and attenuate high levels of oxidative stress.  Because chronic systemic inflammation and oxidative stress have been linked to weight gain, obesity, and metabolic syndrome – it’s possible that oolong tea-mediated reductions of inflammatory mediators and oxidative stress could help promote weight loss.

Metabolic rate increase: There are numerous ways in which oolong tea consumption can directly and indirectly increase your metabolic rate, or the number of calories that your body burns throughout the day.  An increase in metabolic rate after consuming oolong tea may result from: increased thermogenesis (including non-exercise activity thermogenesis); increased fat metabolism; and increased physical activity.

Caffeine within oolong tea is understood to enhance metabolic rate by increasing: fat cell lipolysis (via cAMP-dependent protein kinase A, which activates hormone-sensitive lipase and catalyzes hydrolysis of triglycerides in fat cells); intracellular free Ca2+ levels; and catecholamine secretion from noradrenergic terminals.  Furthermore, if caffeine within oolong tea leads an individual to exercise more frequently – this increase in exercise frequency will increase metabolic rate.

Any increase in metabolic rate relative to baseline (pre-oolong tea consumption) should yield weight loss.  The only way weight loss wouldn’t from an increased metabolic rate is if an individual consumed more calories to compensate for the additional energy loss.

Mood enhancement: Components of oolong tea such as caffeine and polyphenols have been associated with mood enhancement in humans, especially when consumed regularly over a long-term.  Furthermore, research with animal models of depression and anxiety indicates that chronic administration of caffeine and polyphenols can counteract depressive and anxious behaviors.

It is known that depression can alter physiology (to slow metabolic rate, increase fat storage, induce food cravings, etc.); decrease energy level (making it difficult to exercise and burn calories); and can cause some individuals to overeat (as a coping mechanism).  In the event that oolong tea improves your mood (compared to pre-consumption), this mood enhancement (even if modest) may be conducive to weight loss.

Mood enhancement derived from oolong tea components might improve your energy level (resulting in increased physical activity) and negate overeating behavior resulting from depressive states.  Moreover, if you’re in a better mood from oolong tea consumption – you may be more motivated to eat a healthier, lower-calorie diet (than when you were depressed).

Reduce glucose absorption: Polyphenols (e.g. catechins) within oolong tea are hypothesized to inhibit digestive enzymes to reduce glucose absorption.  Research by Shimizu et al. (2000) discovered that tea catechins control dietary glucose uptake at the intestinal tract, and by doing so, they may be capable of normalizing blood glucose concentrations.

According to Williamson (2013), excessive postprandial glucose spikes are a risk factor for diabetes and impaired glucose tolerance, but polyphenols within oolong tea may be capable of inhibiting glucose absorption via SGLT1 and GLUT2 transporters.  Inhibition of glucose absorption via SGLT1 and GLUT2 transporters might indirectly promote weight loss by reducing blood glucose levels – particularly among persons who’ve gained weight and/or are obese.

PEDF modulation: PEDF (Pigment epithelium-derived factor), sometimes referred to as serpin F1, is a protein encoded by the SERPINF1 gene that exerts anti-angiogenic, anti-tumorigenic, and neurotrophic effects.  Research by Crowe et al. (2009) indicates that abnormal serum PEDF and altered PEDF expression in adipocytes can cause insulin resistance, inflammation, increased fat storage, and obesity.

Normalizing serum PEDF concentrations and PEDF adipocyte expression is thought to enhance insulin sensitivity, lower inflammation, and prevent excess fat storage.  Among humans with obesity, it’s possible that PEDF abnormalities may interfere with preexisting weight loss efforts.

Because the polyphenols in oolong tea appear to favorably modulate PEDF in animals with preexisting PEDF abnormalities, it’s reasonable to suspect that similar modulation could occur in humans following oolong tea consumption.  For this reason, PEDF modulation warrants consideration as a potential means by which oolong tea promotes weight loss.

Satiety enhancement: In a small-scale study by Josic et al. (2010) encompassing 14 healthy volunteers, it was discovered that consumption of green tea (300 mL) with breakfast significantly increased subjective ratings of postprandial satiety and fullness, relative to the consumption of water.  Because oolong tea is derived from the same plant (Camellia sinensis) as green tea, it’s not farfetched to expect that a similar effect (increased postprandial satiety) might occur with oolong tea intake.

If postprandial satiety increases from drinking oolong tea with a meal (e.g. breakfast), then this enhanced satiation might prove helpful in reducing calorie intake for the sake of weight loss.  Persons who feel more satiated (i.e. full) as a result of oolong tea consumption will probably be less likely to continue eating (extra calories) after a meal and/or consume unnecessary or extra calories (e.g. in the form of snacks) between meals.

Thermogenesis induction: Research by Hursel and Westerterp-Plantenga (2010) suggests that consuming oolong tea induces thermogenesis, a process by which the body generates heat, increases metabolic rate, and increases energy expenditure.  The induction of thermogenesis is particularly important for persons attempting to lose weight because, when restricting energy intake, metabolic rate tends to decrease; increasing thermogenesis should counteracts some of this metabolic rate reduction.

In addition to inducing thermogenesis (body heat generation), caffeine within oolong tea may enhance non-exercise activity thermogenesis (NEAT).  For general reference, non-exercise activity thermogenesis refers to energy expended for all activities other than sleeping, eating, or engaging in physical exercise; fidgeting or moving throughout the day would be an example of non-exercise activity thermogenesis.

It is estimated that increases in thermogenesis from oolong tea consumption [at sufficient dosages] could burn an extra 300 kJ and 400 kJ per day in select individuals.  Assuming oolong tea-mediated thermogenesis burns an extra 300 kJ per day (relative to homeostatic baseline), this mechanism alone could yield weight loss of 1 lb. in less than 2 weeks (if the oolong tea drinker doesn’t compensate for the energy loss with greater energy intake).

Note: There may be other relevant mechanisms by which oolong tea consumption could induce weight loss.  If you know of any additional mechanisms that could explain weight loss from oolong tea intake – share these mechanisms in the comments section.

Oolong tea & Weight Loss (The Research)

Included below are studies in which the effect of oolong tea on body weight was discussed.  Understand that because oolong tea is not a pharmaceutical drug or a popular dietary supplement, there’s little financial incentive to investigate whether it’s consumption might induce weight loss.

Most preliminary evidence indicates that oolong tea consumption probably supports weight loss via increasing fat oxidation and metabolic rate.  That said, there’s no concrete data from large-scale randomized controlled trials to support the idea that oolong tea consumption is more effective than a placebo for weight loss.

Until additional research is conducted, it’s impossible to state with confidence that drinking oolong tea will induce weight loss or augment preexisting weight loss efforts.  (For additional information about a study listed below, click the hyperlink citation listed as “source” beneath each summary).

2014: Green tea, black tea, and oolong tea polyphenols reduce visceral fat and inflammation in mice fed high-fat, high-sucrose obesogenic diets.

Heber et al. conducted a study to determine the effects of several types of teas (green, black, and oolong) on visceral fat and inflammation in mice fed high-fat, high-sucrose [obesogenic] diets.  Specifically, researchers in this study sought to determine whether decaffeinated polyphenol extracts from green tea, black tea, and oolong tea would reduce body fat and inflammation in male mice (C57BL/6J) receiving high-fat (32%), high-sucrose (25%) diets.

The mice in this study were assigned to receive a high-fat/high-sucrose diet with 0.25% polyphenols (green tea, black tea, or oolong tea) OR a low-fat/high-sucrose diet – for a 20-week duration.  After the 20-week trial, assays revealed the presence of green tea and oolong tea polyphenols in the liver and adipose tissue of mice receiving the high-fat/high-sucrose diet; no black tea polyphenols were discovered.

Among the mice receiving low-fat/high-sucrose diets, polyphenols of all teas (green, oolong, black) led to significant reductions in body weight, visceral fat volume (as evidenced by MRI), and liver lipid weight – compared with mice in the high-fat/high-sucrose group.  It was reported that only green tea polyphenols decreased food intake significantly (~10%).

The ingestion of green tea polyphenols, black tea polyphenols, and oolong tea polyphenols was associated with decreased MCP-1 (monocyte chemotactic protein-1) expression in mesenteric fat.  Furthermore, the ingestion of green tea polyphenols and black tea polyphenols was associated with increased adiponectin gene expression in adipose tissue – indicative of an anti-inflammatory effect.

Oolong tea polyphenol ingestion was also associated with reduced gene expression of pigment epithelium-derived factor (PEDF). (High concentrations of PEDF can cause insulin resistance and lead to obesity).  Researchers concluded that all 3 tea polyphenol extracts (one of which was oolong) induced weight loss, anti-inflammatory, and angiogenic effects.

Overall, this study supports the idea that regular consumption of oolong tea may promote weight loss and/or protect against obesity.  That said, because this study was conducted in animal models of obesity, it is unknown as to whether the findings would be similar in humans who consume oolong tea.

2009: Beneficial effects of oolong tea consumption on diet-induced overweight and obese subjects.

He et al. organized a trial in which 102 individuals (42 males, 60 females) who were either overweight or obese (as a result of hypercaloric diets) received 8 grams of oolong tea per day for 6 weeks.  The aim of this trial was to evaluate the anti-obesity effect of oolong tea in overweight and obese humans.

Before trial initiation, the body fat level, height, and waist circumference of each participant was recorded.  Additionally, the thickness of abdominal subcutaneous fat was documented (3 cm to the right of the navel) with an ultrasonic echo method.

Other measures at baseline included: plasma triglycerides (TG), total cholesterol (TC), and in-vitro pancreatic lipase inhibition.  Participants were also classified by BMI as being: “overweight” (52 participants); “obese” (44 participants); or “severely obese” (6 participants).

After the 6-week trial period, the same measures were collected (body fat, waist circumference, subcutaneous fat, triglycerides, cholesterol, pancreatic lipase inhibition) and compared to baseline.  Results indicated that 70% of “severely obese” (BMI over 35) participants exhibited weight loss exceeding 2.2 lbs. (1 kg) and 22% of this subgroup (severely obese) lost 6.61 lbs. (3 kg) – over the 6-week duration.

A total of 64% of “obese” (BMI 30-35) and 66% of “overweight” (BMI 25-30) participants exhibited weight loss exceeding 2.2 lbs. (1 kg) and subcutaneous fat was reduced significantly in 12% of these subgroups.  A comparison of sexes revealed a stronger correlation between weight loss and subcutaneous fat reduction in males versus females – but a stronger correlation between subcutaneous fat reduction and decreased waist size in females versus males.

Nevertheless, weight loss resulting from oolong tea consumption was associated with waist size reduction in both males and females.  In males, average weight changed from 174.38 lbs. (79.7 kg) to 167.77 lbs. (76.1 kg) – and in females, average weight changed from 154.76 (70.2) kg to 149.47 (67.8 kg).  More specifically, average weight loss in males was ~6.61 lbs. and average weight loss in females was ~5.29 lbs.

Among 22 participants with hyperlipidemia at baseline, concentrations of plasma triglycerides and total cholesterol significantly decreased.  In-vitro assays for pancreatic lipase inhibition indicated that oolong tea may counteract hyperlipidemia via modulation of lipoprotein activity.

Although this was an uncontrolled, moderately-sized trial with Chinese participants, results indicate that oolong tea consumption may decrease body fat and body weight.  Researchers concluded that oolong tea consumption appears to reduce body fat and weight via improving lipid metabolism – and suggest that chronic oolong tea consumption may protect against obesity.

2001: Oolong tea increases metabolic rate and fat oxidation in men.

Rumpler et al. noted that, according to traditional Chinese belief, oolong tea can help control body weight.  In attempt to gauge the accuracy of this popular belief, Rumpler et al. conducted a study to investigate the effect of oolong tea on energy expenditure (EE) in humans.

Researchers organized a randomized trial with a crossover design in which 12 healthy men (ages 25 to 60) consumed 4 treatments: water; full-strength oolong tea (brewed from 15 g of tea); half-strength tea (7.5 g of tea); and caffeinated water (270 mg caffeine – equal to the caffeine concentration in full-strength oolong tea).  For 4 days prior to trial initiation, participants abstained from the consumption of caffeinated beverages and flavonoids.

Additionally, in the 24 hours before trial initiation, all participants underwent a 24-hour calorimeter assessment to determine baseline 24-hour energy expenditure.  Body composition of each participant was also measured at baseline using DEXA (dual-energy X-ray absorptiometry).

Researchers controlled for the feeding of participants by providing a diet that met the RDA (recommended dietary allowance) for essential nutrients and energy (and contained no caffeine).  Treatment blocks were administered over a 3-day period in which participants received the same foods – and one of the 4 treatments: water; full-strength oolong tea; half-strength oolong tea; or caffeinated water – 5 times per day (between 8:30 AM and 2:30 PM).

Results indicated that 24-hour energy expenditure (EE) significantly increased after consumption of full-strength oolong tea (2.9%) and caffeinated water (3.4%) – compared to standard water and half-strength oolong tea.  The increases in energy expenditure equated to ~281 kJ/d (full-strength oolong tea) and ~331 kJ/d (caffeinated water).

It was also reported that fat oxidation significantly increased (~12%) following consumption of full-strength oolong tea – compared to standard non-caffeinated water.  Researchers concluded that oolong tea promotes fat oxidation and increases energy expenditure in normal weight men – and suggested that it may help maintain lower body fat among men who refrain from consuming more food to compensate for the tea-induced fat loss.

1999: Anti-obesity action of oolong tea.

Han et al. conducted a study to determine whether oolong tea consumption is associated with anti-obesity and/or hypolipidemic effects.  The study utilized mice that received high-fat diets to deliberately induce obesity over a 10-week duration.  Mice in the study were divided into two groups: (1) high-fat diet plus oolong tea; and (2) high-fat diet (without oolong tea).

Throughout the study researchers examined the effects of oolong tea components on noradrenaline-induced lipolysis.  Results of the study indicated that the average food consumption (i.e. calorie intake) did not differ between the two groups of mice throughout the 10-week study.

However, the mice that received oolong tea (in addition to the high-fat diet) were protected against obesity and fatty liver induced by a high-fat diet.  Researchers pinpointed that the caffeine within oolong tea bolstered noradrenaline-induced lipolysis in fat cells, accelerated hormone-induced lipolysis, and inhibited activation of pancreatic lipase.

It was concluded that oolong tea exerts an anti-obesity effect in mice consuming high-fat diets – likely through enhancement of noradrenaline-induced lipolysis (facilitated by caffeine) and inhibition of pancreatic lipase activation (facilitated by an unknown oolong tea component).  Researchers suggested that oolong tea could be effective for the treatment of obesity and fatty liver resulting from high-fat diets.

Note: If you’re aware an additional study in which the effect of oolong tea on body weight and/or body fat was examined, feel free to share and/or discuss the study in the comments section of this article.

Limitations associated with research of Oolong tea for weight loss

There are some significant limitations associated with the research of oolong tea for weight loss that warrant mentioning.  The most significant limitation associated with research of oolong tea for weight loss is that only 2 studies have been conducted in humans in attempt to determine its effect on body weight – neither of which were of high quality.

  • Animal models: Nearly half of the data suggesting that oolong tea promotes weight loss (or fat loss) is derived from research in which oolong tea polyphenols were administered animal models of obesity (mice fed high-fat diets). Although oolong tea polyphenols appear to prevent weight gain and obesity in mice, we cannot extrapolate these findings to humans.  Many compounds that promote weight loss (or have beneficial health effects) in animal models fail to yield the same effects in humans.
  • Burning more calories vs. weight loss: Although oolong tea may promote increased energy expenditure in a subset of consumers (when ingested at an adequate dose), the increased energy expenditure will not result in weight loss if offset with increased energy intake. In other words, if someone trying to lose weight burns more calories with oolong tea – but they consume more also (due to lack of appetite control), weight loss will not occur.  No research has been conducted to determine if oolong tea consumers may simply eat more calories to counteract tea-mediated increases in energy expenditure, ultimately negating weight loss.
  • Limited human research: As of 2018, there are only 2 trials that have investigated the specific effect of oolong tea on aspects of human physiology relevant to weight loss. One of these studies was extremely short-term (investigating 24-hour energy expenditure over a period of 4 days after consumption of oolong tea preparations) with a small sample size (12 men) and the other had no placebo-control – despite being conducted over a longer-term (6 weeks) and having a larger sample (102 participants).
  • Oolong tea vs. caffeine (standalone): While oolong tea polyphenols may alter physiology in ways that promote weight loss, most evidence suggests that caffeine is the primary driver of oolong tea-mediated weight loss. In fact, one study found that caffeinated water (with an equivalent amount of caffeine as oolong tea) generated greater 24-hour energy expenditure versus oolong tea.  This suggests that there may be nothing special about oolong tea (other than its caffeine content) for weight loss.

Variables that may influence Oolong tea-induced weight loss

There are many variables that could determine how much weight you lose from drinking oolong tea.  Variables that will probably influence the amount of weight that you lose from oolong tea consumption include: oolong tea dosage (i.e. strength/quantity consumed); duration of oolong tea consumption (e.g. short-term vs. long-term); concurrent substance use; and individual factors (body size, genetics, lifestyle, medical conditions, etc.).

  1. Oolong tea dosage (per day)

The dosage of oolong tea that you consume (contents of caffeine, polyphenols, catechins, etc.) per day may influence whether you’ll experience weight loss.  One human study reported that full-strength oolong tea (prepared with 15 grams) significantly increased 24-hour energy expenditure – but that half-strength oolong tea (prepared with 7.5 grams) did not.

Generally, the greater the dosage of oolong tea that you ingest each day – the more likely it’ll be that you’ll lose weight (assuming you’re capable of losing weight on oolong tea).  Larger doses of oolong tea will contain more caffeine and polyphenols for stronger physiologic modulation than smaller doses.

  1. Frequency & duration of oolong tea consumption

The frequency & duration of oolong tea consumption could determine whether you end up losing weight from its consumption – and/or the amount of weight that you lose.  In terms of frequency, someone who drinks oolong tea sporadically (e.g. once every other week) probably won’t lose much (if any) weight from its consumption – due to lack of a consistent, long-term physiologic effect.

However, someone who drinks oolong tea every single day (and/or multiple times per day) will probably derive a consistent, long-term physiologic effect from its frequent ingestion – increasing the likelihood of weight loss.  Assuming you’re drinking an adequate dosage of oolong tea on a daily basis – the total duration of your consumption could determine how much weight loss you experience.

Some studies suggest that oolong tea may increase metabolic rate by 300 kJ to 400 kJ per day.  If this is the case, then it may take nearly 2 weeks to lose 1 lb. (assuming you aren’t overeating to make up for the calorie deficit).  To experience noticeable or substantial weight loss from oolong tea consumption, it’s likely that you’ll need to drink it over an extended duration (e.g. months); weight loss is not usually immediate (other than possible water weight loss from a diuretic effect).

  1. Use of substances with oolong tea

In the event that you’re using substances with oolong tea (medications, supplements, etc.) – there’s a chance that these substances might: counteract OR enhance the weight loss effect of oolong tea.  An example of a substance that might counteract the weight loss effect of oolong tea is Zyprexa (i.e. olanzapine), an antipsychotic medication.

Zyprexa is known to increase pathogenic gut bacteria, decrease energy levels, increase fat storage, and slow metabolic rate – all of which yield weight gain.  These actions of Zyprexa may counteract or override the actions by which oolong tea promotes weight loss – such that weight loss won’t occur from oolong tea consumption.

An example of a substance that might enhance the weight loss effect of oolong tea is Adderall (i.e. mixed amphetamine salts).  Adderall is understood to suppress appetite, increase energy levels, accelerate fat burning, and increase metabolic rate – all of which promote weight loss.

The actions of Adderall may augment or complement the actions by which oolong tea promotes weight loss – such that greater weight loss occurs from the combination (than would’ve occurred with standalone oolong tea).  If you are losing more or less weight than you expected from oolong tea consumption – reflect upon the possible influence of concomitant substances.

  1. Oolong tea drinker (individual factors)

Factors associated with the specific person drinking oolong tea could determine how much weight is lost from oolong tea consumption.  User-specific factors that might affect the magnitude of weight loss from oolong tea consumption include: age, body size, calorie intake, genetics, lifestyle, medical conditions, prior substance use, sex, and tolerance (particularly to caffeine).

  • Age: The effects of oolong tea may vary depending on the age of the consumer. It is understood that caffeine metabolism can change with age – due to changes in blood flow and organ function (liver and kidneys).  It’s possible that certain age groups may be more responsive to the physiologic effects of oolong than other age groups such that weight loss is more likely to occur.
  • Body size: Larger individuals generally have higher body weights than smaller individuals. For this reason, larger individuals will probably experience greater total weight loss (on average) from oolong tea consumption than smaller persons.  Additionally, persons with high BMIs will probably experience greater weight loss from oolong tea consumption because persons with normal BMIs have less weight to lose.
  • Calorie intake: The number of calories that you consume in a day could determine how much weight you lose from oolong tea consumption. If oolong tea helps you burn extra calories, but you increase your calorie intake to compensate for those extra calories burned – you won’t lose weight.
  • Genetics: It is known that genetic differences can influence caffeine metabolism – and possibly other physiologic reactions to oolong tea constituents (e.g. polyphenols). This considered, it’s possible that genetic differences might account for weight loss differences following oolong tea consumption.
  • Lifestyle: Healthy lifestyle habits such as eating a balanced diet, minimizing stress, getting adequate sleep, and exercising might augment the effects of oolong tea to promote weight loss – whereas unhealthy habits may override its weight loss effects.
  • Medical conditions: Preexisting medical conditions could influence whether you have success using oolong tea for weight loss. Certain medical conditions might make weight loss very unlikely with oolong tea – compared to healthy individuals (devoid of medical conditions).
  • Prior substance use: Using substances prior to initiating regular consumption of oolong tea could determine how much weight is lost while regularly consuming oolong tea. For example, recent discontinuation of an agent that caused weight gain or weigh loss – will probably result in weight loss or weight gain, respectively, as a result of physiology reverting back to homeostasis (and this may be misattributed to oolong’s influence).
  • Sex: One study reported that while oolong tea promotes weight loss in men and women, the amount of weight loss (relative to baseline body weight) was slightly greater in women.  Based on this finding, it’s possible that the magnitude of physiologic effects resulting from oolong tea consumption might vary depending on sex.
  • Tolerance: Because caffeine may be the most important component of oolong tea for induction of weight loss – it’s possible that high caffeine tolerance might minimize likelihood of weight loss that may result from oolong tea. If caffeine tolerance is high, it may have a less significant impact on fat metabolism, metabolic rate, and energy levels – than it would have in persons with zero or low tolerance.
  • Water retention: Someone with high water retention (due to high dietary sodium intake or edema) might lose more weight with oolong tea consumption than someone with less substantial water retention. The diuretic effect of caffeine (within oolong tea) may yield a significant water weight loss in a person carrying a lot of water weight – relative to persons carrying less water weight.

Recommended Oolong tea products

Below are several oolong tea products that I personally recommend for persons who want to try oolong tea [out of curiosity, for weight loss, or to attain potential benefits].  Understand that you may want to discuss oolong tea consumption with a medical doctor to ensure that it won’t interact with any medications and/or supplements that you’re using – or pose any health risk.

Affiliate disclosure: The links to the oolong tea products below are affiliate links – meaning I’ll earn a small commission if you purchase through my link.  If you found the article helpful and want to try oolong tea – I’d genuinely appreciate you purchasing through my affiliate link (it’s the same price either way).

  1. Davison’s Oolong Tea (Chinese) – This is a quality loose leaf oolong tea from China.

  2. Oolong Loose Tea Leaves (Taiwanese) – This is a quality loose leaf oolong tea from Taiwan.

  3. 100% Organic Oolong – This is a low-cost oolong tea (100 bags for ~$7) for those who don’t want to buy loose-leaf formats

Have you lost weight drinking oolong tea?

If you’ve been consuming oolong tea regularly (at a reasonable strength/dose), feel free to leave a comment sharing whether you’ve lost weight (or were unable to lose weight).  Assuming you lost weight from drinking oolong tea, report the approximate amount of weight that you lost and whether (from what you’ve observed) this weight loss is: water weight; fat loss; and/or muscle loss.

For persons who lost weight with oolong tea consumption – how long did it take to experience noticeable weight loss?  Did your weight loss eventually peak and stabilize (such that you were unable to lose additional weight after a specific duration)?  (If your weight loss peaked, how long did it take to reach this peak?)  While drinking oolong tea, did you engage in other activities or behaviors that are conductive to weight loss such as: consuming a hypocaloric diet and/or engaging in exercise?

To help others get a better understanding of your situation, provide details in your comment such as: your daily oolong tea dose; frequency of consumption (every day); concurrent substance use (medications, supplements, etc.); your BMI before using oolong tea versus after; and any preexisting medical conditions that might be affecting your body weight.  Are you satisfied with the amount of weight you’ve lost since drinking oolong tea?

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