With millions of people already fighting excess weight and estimates for nearly half of all adults in the US to be living with obesity by 2030, affected patients need all the assistance they can get in this most difficult struggle. Beyond the dietary and lifestyle strategies that are known to improve metabolic health and aid in fat loss, an array of phytochemicals and other compounds have been shown to be effective for regulating appetite in some subjects, which has potential implications for supporting fat loss. Let’s examine the effects of green tea extract with regard to appetite.
A recent article on compounds that may be helpful for obesity explored the thermogenic properties of EGCg (epigallocatechin gallate), one of the primary polyphenols in green tea extract, noting that EGCg enhances fat oxidation and increases energy expenditure—and these effects are independent of the caffeine content. Beyond these effects, EGCg may help control appetite, a factor that cannot be ignored in the realm of fat loss. For some people, willpower is a finite resource. Patients can only be expected to white-knuckle through hunger pangs for so long. Advice to limit food intake—the amount as well as the timing—without addressing hunger is a losing proposition.
A randomized, double-blind crossover study evaluated the effects of 752mg EGCg compared to 800mg corn starch (used as placebo) on gastric emptying in healthy women with a normal body mass index (BMI). The treatments were taken along with a liquid test meal (280 calories, 20% protein, 20% fat, 60% carb) and gastric emptying, perception of hunger, desire to eat, and satiation were assessed at baseline (fasted) and at 30, 90 and 150 minutes after supplementation. (Glucose, insulin, leptin and adiponectin were also measured.) No significant differences were found between EGCg and placebo for glucose, insulin, or leptin, but adiponectin was higher at 150 minutes in the EGCg group, and EGCg delayed gastric emptying. Subjects who took EGCg reported greater satiation at 90 minutes. Unfortunately, overall, this did not result in a significant difference in hunger or desire to eat, but the numbers reported were the means: individual subjects may have responded more powerfully, so it may be that for some individuals, but not all, EGCg could be helpful for modestly controlling appetite. Results also may have been different if test subjects had obesity or if the test meal had consisted of solid food.
A separate randomized controlled trial looking at the effects of green tea on postprandial blood glucose, insulin and satiety in healthy subjects found that green tea did affect blood glucose, but not in the way you would think: compared to a test meal of white bread and sliced turkey with water, the same meal with green tea (300mL or ~10fl oz) resulted in higher plasma glucose levels at 120 minutes, although there were no differences in total area under curve for glucose and insulin. So green tea had no influence on decreasing glucose or insulin compared to water, but subjects drinking green tea reported increased fullness and satiety, which could have implications for reducing food intake at subsequent meals. This study employed green tea rather than isolated EGCg, and the flavor of the beverage may have had an influence on satiety and perceived fullness. Again, however, considering the difficulty many people have in losing excess body fat, any advantage, however small, may be useful, especially one as inexpensive as drinking green tea.
A 2019 systematic review of the effect of various bioactive phytochemicals on suppressing appetite and increasing satiety found that results for EGCg were inconclusive. Some studies showed no significant difference between EGCg and placebo in modulating appetite, hunger, fullness, or satiety, but a few studies did report benefits in one or more of these parameters. It may be that certain subjects respond favorably while others are non-responders. For those who do experience noticeably increased satiety, EGCg could be a useful adjunct in weight loss.
What about after losing weight? As many people can attest, maintaining a lower body fat mass may be even more difficult than taking excess fat off in the first place. Green tea catechins (plus caffeine) may be beneficial for helping to reduce the likelihood of weight regain by counteracting the decrease in metabolic rate that often occurs during weight loss. (Low carbohydrate diets have been shown to potentially have a similar effect in preserving or perhaps even increasing metabolic rate [energy expenditure] after weight loss.)