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Caffeine and Weight Loss

Katie Girardi

October 10, 2008


Main Idea:

            Today in the United States, Obesity is a widespread health problem.  It is no surprise that new claims about ways to lose weight are constantly being made.  New diets, supplements, and exercise regimens are always being advertised on television and in magazines.  One such claim is that drinking caffeinated beverages, like teas and coffee, can help you lose weight.  Multiple reliable scientific studies have concluded that there is a moderate correlation between the amount of caffeine in your diet and increased weight loss. 

Health Risks of Obesity:

            Being obese has many serious health implications, including increased risk for heart disease, high blood pressure, type-two diabetes, sleep apnea, stroke, and arthritis.  Individuals who are considered obese have a Body Mass Index of 30 or higher, and losing weight would seriously improve the quality of their life and their overall health.  Obesity is generally caused by a combination of genetic predisposition to the condition and lifestyle choices (  Since it is impossible to change your genetics, it is especially important to understand how to control your weight through behaviors, like diet and exercise.  Seeing as the media is constantly bombarding us with different strategies to lose weight, how do we know which claims are true?  Multiple recent studies demonstrate that caffeine has positive health benefits, once of which is increased weight loss. 

What exactly is caffeine?

            Caffeine is a bitter tasting crystalline powder.  The chemical makeup of caffeine is C8H10N4O2 and medically it is referred to as trimethylxanthine.  It is a mild diuretic and effective cardiac stimulant ( 



Typically, brewed coffee contains 100 mg of caffeine in every 6-ounce serving, tea contains 70 mg of caffeine in every 6-ounce serving, and colas contain around 50 mg of caffeine in every 12-ounce serving, so it is no surprise that over half of the American population consumes more than 300 mg of caffeine every day without realizing it (  Since caffeine is common in so many foods and drinks Americans consume on a daily basis, understanding the impact caffeine has on health is particularly important. 

Caffeine and Thermogenesis:

            Thermogenesis is the process through which the body’s metabolic activity increases and the body generates heat (  Thermogenesis is activated naturally through exposure to cold and exercise.  It can also be activated through consuming certain nutrients like caffeine.  According to Diepvans et al, “the stimulatory effect of caffeine on thermogenesis in man is well established” (2007, page 77).  Caffeine affects thermogenesis by inhibiting the phosphodiesterase-induced degrading of cyclic AMP (Diepvans, 2007).  Since cyclic AMP is an important molecule that helps regulate metabolic activity, inhibiting the break down of cyclic AMP helps stimulate the metabolism (  Stimulating the metabolism is essential for effective weight loss. 

Scientific Studies Concerning Caffeine and Weight Loss:

Study 1:

            Westerterp-Plantenga et al investigated the effects of caffeine on weight loss and weight maintenance.  Their primary hypothesis was that the green tea-caffeine mixture would reduce body weight regain after weight loss (Westerterp-Plantenga, 2005).  They designed a double-blind study in order to ensure accuracy.  Both male and female subjects between 18 and 60 years old who had Body Mass Indexes between 25 and 35 were recruited for the study.  After further medical examination, participants were eliminated.  Only those who were in good health, did not smoke, were not on medication, and consumed alcohol moderately if at all were eligible.   After excluding the ineligible participants, 76 subjects participated in the study.  During the first phase, or weight loss phase of the study, all participants were put on a low energy diet for four weeks.  During those 4 weeks, they consumed modifast for three meals each day.  Modifast contains 50 g of carbohydrates, 52 g of protein, and 7 g of fat.  The modifast packets were to be dissolved in milkshakes, soups, or pudding.  In addition to those three meals participants were allowed to eat as many fruits and vegetables as they wanted.  Each participant was expected to lose at least 4 kg.  After the four-week weight loss phase, the weight maintenance phase began.   During the weight maintenance phase subjects were broken up into two categories, high caffeine consumers or low caffeine consumers.  High caffeine consumers regularly consumed over 300 mg of caffeine each day, while low caffeine consumers regularly consumed less than 300 mg of caffeine each day.  Once those groups were determined, half of the participants in each category were given the experimental capsule and the other half was given a placebo.  The experimental capsule contained caffeine, epigallocatechin gallate, and vegetable oil and the placebo only contained vegitable oil.  Measurements were taken every month for three months to determine weight loss and weight maintenance.  Those measurements were then compared to the baseline measurements taken before the weight loss phase.

            At the culmination of the study, Westerterp-Plantenga et al concluded that high caffeine intake was associated with weight loss.  They inferred that the effect of caffeine increased thermogenesis and fat oxidation while suppressing leptin, a hormone that regulates metabolism and body weight (Westerterp-Plantenga, 2005).  Interestingly, during the weight loss phase of the experiment, habitually high caffeine consumers lost more weight.  However, during the weight maintenance phase, the group that habitually consumed less caffeine and received the green tea-caffeine supplement was most successful at keeping the weight off.  This group also continued to lose weight during the maintenance phase, compared to the placebo group, which did not continue to lose weight.


Study 2:

            Greenberg et al conducted a longitudinal follow up study using participants, both male and female, ranging in age from 25 to 75.  The purpose of their study was to analyze how caffeine affected body weight and diabetes risk.  In order to do this they used the National Health and Nutrition Examination Survey Epidemiological Follow Up Study, which contained data including the consumption levels of various beverages and body weight measurements (Greenberg, 2005).  The first phase of the study was conducted from 1971 until 1975, and then there were four follow up studies.  The first was conducted from 1984 until 1984 and then the rest were conducted in 1986, 1987, and 1992.  During the second phase of the study, participants who were missing data or reported a history of diabetes were excluded.  After the exclusions, Greenberg et al analyzed data from 7006 subjects ranging in age from 32 to 87 years old.  The body weight of all participants was measured during each follow up study, and their Body Mass Indexes were calculated.  Each participant’s snack and beverage intake was determined to see how much caffeine they consumed each day.  They also accounted for an American style diet, gender, race, education, smoking, alcohol consumption, and physical activity.  Ultimately four categories were determined for analysis; ground caffeinated coffee drinkers younger than 60 years old, ground caffeinated coffee non-drinkers younger than 60 years old, ground caffeinated coffee drinkers older than 60 years old, and ground caffeinated coffee non-drinkers older than 60 years old. 

            After data analysis, Greenberg et al concluded that increased weight loss and decreased risk of diabetes could only be shown for the participants who were younger than 60 years old.  In the younger than 60 age group, higher beverage consumption was correlated with increased weight loss (Greenberg, 2005).  Interestingly, both ground caffeinated coffee and ground decaffeinated coffee increased the likelihood of weight loss.  This statistic demonstrates that it might not necessarily be the caffeine component of coffee that increases weight loss. 

            The information presented in this study might not be as reliable as the information presented in the Westerterp-Plantenga et al study.  Greenberg et al uses an impressively large sample size, which usually leads to more conclusive results.  However, they relied on self-reports to determine their participant’s diets during the course of the study.  Then to determine the amount of caffeine the participants consumed, researchers used the average amount of caffeine in the foods and beverages their subjects consumed each day.  Since the participants could have been inaccurate in their reports of the foods and drinks they consumed, and they could have misreported the amount of food or drink they consumed, the results of the study could be inaccurate.  In the other studies, though the sample size was smaller, their diets were more controlled, which could lead to more accurate results.

Study 3:

            Auvichayapat et al conducted a study that investigated the effects of green tea on weight reduction in obese Thais (2007).  In this study, 60 obese Thai subjects with a Body Mass Index greater than 25 participated.  All participants were between 40 and 60 years old, and female participants had to be postmenopausal for over one year.  The study excluded anyone with metabolic disease, such as diabetes, thyroid disease, and crushing syndrome.  Those with any systemic disease, history of caffeine sensitivity, taking prescription medication or hormone therapy were also excluded.   Another requirement for participants was their average total energy expenditure had to be more than 8373.6 kJ per day.  The participants were randomly selected to be part of the green tea group or the control group.  Participants in the green tea group took a green tea capsule, which contained 28.86 mg of caffeine, after breakfast, lunch, and dinner.  The participants in the control group took a cellulose capsule after every meal.  Throughout the experiment, subject’s diets were regulated; every meal was prepared by the Nutrition Unit of Srinagarind Hospital to ensure that each participant consumed 8373.6 kJ of total energy each day.  Measurements were taken at baseline, the fourth week, eighth week, and twelfth week.  Body Mass Index, energy expenditure, substrate oxidation and body composition were all measured at each follow up.  Urine VMA and serum leptin levels were measured at baseline and at the end of the twelfth week. 

            The Auvichayapat et al study found that, “green tea capsules in a dosage of 100 mg each day can increase energy expenditure and fat oxidation in obese Thai subjects in a 12 week period” (2007, page 490).  Since increased energy expenditure and fat oxidation contribute to greater weight loss, they concluded that caffeine could contribute to increased weight loss.  However, it is important to note that all of these test subjects were Thai, and caffeine intake in general among the Thai population is far less than the caffeine intake of the American population.  For this reason, the results of this study might not be able to be effectively applied to the American population. 

Study 4:

            Belza et al investigated the effect of a supplement that contained, tyrosine, capsaicin, catechines, and caffeine on thermogenesis, body fat loss, and fecal fat excretion (Belza, 2007).  In order to carry out this experiment, 93 overweight but otherwise healthy adults with an average Body Mass Index of 31.3 and an average age of 46.2 years old participated.  All participants had to be nonathletic, nonsmokers, who were on no prescription medication.  All participants also followed an average Danish diet with rare consumption of hot spices, coffee, and tea.  The study lasted for 12 weeks.  The first four weeks of the study were designated for weight loss.  During this period all participants followed a 3.4 MJ per day diet, consisting of six meals of a 37 g formula in 250 ml of water.  By the end of the weight loss period, if participants did not lose the required 4% of their initial body weight, they were excluded from the study.  The remaining 80 subjects were randomized into three categories.  One group received a placebo, one received a simple release bioactive supplement, and the last received an enterocoated release bioactive supplement.  The only difference between the supplements was the release form.  Both experimental supplements contained green tea extracts and caffeine among other ingredients, and the placebo contained cellulose.  All participants were instructed to take their supplement one hour before each meal.  Through taking the supplement, the experimental groups received a 302 mg dose of caffeine each day.  During the weight maintenance phase all subjects were instructed to consume a diet that would result in a 1250 kJ per day energy deficit.  The participant’s body weight, waist/hip circumference, and blood pressure were measured every four weeks during the study.  Body composition, fat mass, and fat free mass were measured at the beginning and end of the weight loss period and again at the end of the entire study.  Participant’s respiratory measurements, fecal samples, and urine samples were also collected throughout the study. 

            This particular study concluded that the bioactive supplement successfully increased thermogenesis by 90 kJ more than the placebo.  As a result, the experimental groups, those who received the supplement, had more fat mass reduction (Belza, 2007).  This study is particularly accurate because, as a compliance indicator, every two weeks all subjects returned their pill bottles to the researchers so their remaining pills could be counted.   Although compliance in terms of taking the capsules was accounted for, compliance in terms of participant’s diets was not accounted for.  Participants received extensive information on the diet they should have been adhering to, but there was no way to assess whether or not they were following the regimen. 

Other Evidence Explaining the Role of Caffeine in Weight Loss:

            Numerous other studies also explored the role of caffeine in weight loss.  Greenberg et al conducted a meta-analysis study during which they compiled 21 studies that investigated the links between caffeine, weight loss, and protection against diabetes.  The over all conclusion of this meta-analysis was, “both caffeine and coffee intakes were modestly and inversely associated with weight gain” (Greenberg, 2006).  However, it is important to note that, not every study reported this positive effect of caffeine.  Three studies reported no significant effects of caffeine, and some studies only noted positive effects of caffeine during participant’s weight maintenance (Greenberg 2006).  

Why is Weight Loss so Important?

            Obesity not only affects many individual’s self-confidence and quality of life, it is also a risk factor for various major health problems.  Coronary heart disease, type two diabetes, gallstones, and many types of cancer are more common in people who are overweight (  Overweight individuals could significantly reduce their risk of developing the ailments associated with obesity by reducing their body weight by as little as 10 percent (  Since caffeine intake can modestly help individuals lose weight and maintain their weight loss, and losing as little as 10 percent of your current body weight can considerably reduce your risk for health conditions associated with obesity, it is worthwhile to pay attention to your caffeine ingestion. 

Overall Conclusions:

            Through analysis of multiple scientific studies, it is apparent that there is a mild correlation between caffeine consumption and weight loss.  However, it is important to keep in mind that consuming caffeine alone will generally not contribute to significant weight loss.  The safest and most effective way to lose weight is to increase the amount of exercise and physical activity you do, while monitoring your diet (  While modifying your eating and exercise habits, caffeine consumption, through foods, beverages, or supplements, can help with added weight loss and weight maintenance.  More research is needed to determine the exact health benefits of caffeine. 







Literature Cited:

Auvichayapat, Paradee. "Effectiveness of Green Tea on Weight Reduction in Obese         Thais: A Randomized, Controlled Trial." Physiology and Behavior (2007): 486-      91.


Belza, A., E. Frandsen, and J. Kondrup. "Body Fat Loss Achieved By Stimulation of                   Thermogenesis." International Journal of Obesity (2006): 120-30.


Diepvens, Kristel, Klaas R. Westerterp, and Margriet S. Westerterp-Plantenga. "Obesity    and Thermogenesis related to the Consumption of Caffeine, Ephedrine, Capsaicin,        and Green Tea." The American Journal of Physiology (2007): 77-85.


Greenberg, J. A., K. V. Axen, R. Schnoll, and C. N. Boozer. "Coffee, Tea and Diabetes:   The Role of Weight Loss and Caffeine." International Journal of Obesity (2005):        1121-129.


Greenberg, Jacob A., Carol N. Boozer, and Allan Geliebter. "Coffee, Diabetes, and           Weight Control." The American Journal of Clinical Nutrition (2006): 682-93.


Westerterp-Plantenga, Margriet S., Manuela P. Lejeune, and Eva M. Kovacs. "Body          Weight Loss and Weight Maintenance in Relation to Habitual Caffeine Intake and     Green Tea Supplementation." Obesity Research (2005): 1195-204.




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