Introduction
Obesity is a growing global health concern linked to various health issues, including type 2 diabetes, cardiovascular disease, and certain cancers. While various strategies exist for managing weight, including lifestyle changes and prescription drugs, alternative medicines, particularly natural botanicals, are gaining attention due to their perceived effectiveness and safety. Green bean coffee extract (GBCE), containing chlorogenic acid (CGA), is one such natural botanical believed to aid in weight loss. This article explores the research surrounding coffee and its additives, specifically GBCE and CGA, and their potential impact on weight management.
The Potential of Green Bean Coffee Extract (GBCE)
Green coffee beans contain potent nutrients and bioactive substances, including caffeine, caffeic acid, and chlorogenic acids (CGA), and is currently believed to help with weight loss. Many clinical trials support that GBC is associated with reducing the risk of insulin resistance, obesity, and anti-inflammatory and antioxidant properties and has been found to be safe for consumption. CGA exhibits antidiabetic, anti-lipidemic, and anti-obesity properties since they regulate glucose and lipid metabolism and inhibit lipid absorption. CGA and caffeic acid were suggested to improve body weight, lipid metabolism, and obesity-related hormone levels in high-fat diet-induced mice, which may through changing plasma adipokine level and body fat distribution and suppressing the activities of fatty acid synthase, 3-hydroxy-3-methylglutaryl coenzyme-A reductase (HMGCR), and acyl-CoA:cholesterol acyltransferase (ACAT), whereas stimulating fatty acid β-oxidation activity and peroxisome proliferator-activated receptors (PPARα) expression in the liver. Additionally, CGA diminish body weight and fat deposition which may be related to peroxisome proliferator-activated receptor gamma, coactivator 1α (PGC-1α), and uncoupling Protein 1 (UCP1) in the monosodium glutamate (MSG)-induced obesity mouse model and the oleic acid-induced HepG2 cells.
Meta-Analysis of GBCE and Body Weight
According to a meta-analysis, GBCE with CGA 500 mg/day lowers body weight. The meta-analysis included three RCTs with 103 individuals (case = 51, control = 52). The combined findings of GBCE with CGA at least 500 mg/day result in body weight reduction (WMD: − 1.30 and 95% CI: − 2.07 to − 0.52, p = 0.001) without study heterogeneity (I2 = 0%, p = 0.904) and without publication bias estimated using Egger’s and Begger’s test (p = 0.752 and p = 0.602, respectively).
How Coffee and Caffeine Impact Weight Management
Coffee and caffeine have been rumored to be a quick, easy weight-loss fix. The rationale is partly linked to coffee’s ability to get the digestive system moving. The caffeine in coffee can ramp up muscle contractions in the colon that stimulate bowel movements. That means the digestive system clears its contents a little quicker than usual. Caffeine is also a diuretic, meaning it increases urine production, and peeing more causes a loss of water weight. These combined effects on digestion and water weight happen quickly after consuming coffee but are short-lived-they don’t cause permanent weight loss.
Drinking coffee regularly doesn’t lead to significant weight loss, but it may prevent weight gain-albeit modestly. The average person typically gains weight as they get older-about a pound per year through middle age-but avid coffee drinkers seem to experience less age-related weight gain. A 2023 study followed the coffee habits of more than 150,000 participants and found that drinking unsweetened coffee was associated with a modest reduction in weight gain over four years after adjusting for other lifestyle variables. With each additional cup, the coffee drinkers gained about a quarter of a pound less than their peers. Most people probably won’t feel such a small difference in weight, though. Other studies have reported similar results.
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Coffee has also been linked to a small loss of body fat. In one study, people who drank four cups of instant coffee a day had 4 percent less fat mass. They also lost a small amount of their total weight after a period of almost six months. That’s compared with a placebo group that drank a beverage that looked and tasted like coffee and maintained similar diet and exercise habits.
Caffeine, the primary bioactive compound in coffee, appears to be one of the main drivers of the reduced weight gain. The compound is known to stimulate diet-induced thermogenesis-the energy used to digest, absorb and store nutrients from food. On average, people spend about 10 percent of their total energy expenditure processing food. Studies have shown that caffeine can increase that amount by raising a person’s metabolic rate. A higher metabolic rate causes the body to use more energy at rest. The digestive process speeds up, causing organs in the gut to use slightly more energy and burn more calories. Overall, this energy increase is small, however: coffee drinkers might burn 80 to 150 more calories per day, according to one short-term study. That’s equivalent to a few Oreo cookies-but those few extra lost calories can add up over time, Hu says.
Caffeine is also believed to stimulate the sympathetic nervous system, which regulates the body’s fight-or-flight response. It blocks receptors that bind adenosine, a neurotransmitter that triggers feelings of sleepiness and promotes relaxation. Caffeine then prompts physiological responses in the sympathetic nervous system such as increased heart rate and alertness. That, in turn, burns slightly more calories, explains Marilyn Cornelis, an associate professor of preventive medicine at Northwestern University. Caffeine may also increase fat oxidation-the process of breaking down fat stored in tissues for energy-which might explain why coffee consumption is associated with a decrease in fat mass.
The Role of Chlorogenic Acid (CGA)
Independent of caffeine, coffee also contains several polyphenols-a type of antioxidant-that might affect weight. Chlorogenic acid, the polyphenol that gives coffee its distinctly bitter taste and strong aroma, has been shown to help maintain stable blood glucose levels. Because food cravings can be related to blood sugar fluctuations, more stable blood sugar might also help regulate appetite, Cornelis says. The bitter taste itself could also play a role; there’s evidence that the gut senses bitter compounds and adjusts appetite hormones to reduce food intake.
Scientists are only beginning to understand how chlorogenic acid may enhance coffee’s effect on hormones that control appetite and hunger. One small study that followed 126 people who were considered overweight found that coffee had a regulatory effect on satiety hormones; people ate slightly less and felt fuller after drinking the beverage. After drinking coffee, participants had higher levels of serotonin, a brain chemical that, among other things, can suppress appetite, and lower levels of the hunger-inducing hormone ghrelin. These effects were stronger in those who drank the coffee blend that contained more chlorogenic acid. The evidence suggests that coffee might influence appetite and hunger, but it may vary immensely from person to person. So drinking coffee to immediately suppress a spike in hunger may not be a realistic expectation.
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Cafestol and its Effects on Metabolic Health
Cafestol is a natural diterpene compound found in coffee, particularly coffee brewed through unfiltered methods, such as boiled, Turkish, French press, and espresso coffee. In a randomized controlled trial, researchers aimed to assess whether pure cafestol affects insulin sensitivity and glucose tolerance in healthy individuals with high waist circumference, which is a diabetes risk factor. The study’s findings suggest that 6 milligrams (mg) of cafestol twice daily for 12 weeks may lead to slight weight and body fat loss, but not significantly improve insulin sensitivity or glucose tolerance.
Specifically, participants who took cafestol lost about 880 grams (g) of weight, while those on the placebo gained 920 g. Those who took cafestol had an average 400-milliliter decrease in visceral fat volume. Cafestol also seemed to change how fat was processed in the body. The cafestol group exhibited higher initial free fatty acid levels following the intervention, potentially suggesting an undesirable increase in insulin resistance in fat tissues. The study reported no harmful liver or kidney changes, though one person with infectious mononucleosis (mono) had a slight increase in a liver enzyme. Some people experienced side effects like gas, nausea, loose stools, and mild headaches.
Lightly Roasted Coffee and its Impact on Body Composition
A study analyzes the effects on body composition and variables related to metabolic syndrome of two coffees with different degree of roasting and phenolic content. Sixty participants with body mass index between 25 and 35 kg/m2 and a median age of 51.0 years (Interquartile range 46.3-56) were recruited. The study was a controlled, randomized, single-blind crossover trial consisting in drinking three cups/day of roasted coffee (RC) or lightly roasted coffee (LRC) during 12 weeks with 2-week wash-out stages before each coffee intervention. LRC contained ≈400 mg of hydroxycinnamic acids and ≈130 mg of caffeine per 200 mL/cup while RC contained ≈150 mg of hydroxycinnamic acids and ≈70 mg of caffeine per 200 mL/cup.
After the consumption of both coffees, fat mass and body fat percentage (LRC: −1.4%, p < 0.001; RC: −1.0%, p = 0.005) were reduced, whereas muscle mass and muscle mass percentage slightly increased (LRC: 0.8%, p < 0.001; RC: 0.7%, p = 0.002). The decrease in fat percentage was greater with LRC compared to RC (−0.8%; p = 0.029). There were no significant changes in metabolic syndrome variables or in body weight.
Coffee and Exercise
A 2021 review indicated that coffee seemed to have a positive effect on exercise and physical endurance. Researchers listed some of the following benefits: muscular endurance, movement speed, and muscular strength. If consumed in doses of 3 to 6 milligrams per kilogram (mg/kg ) of body mass, caffeine intake enhanced exercise performance in individuals. Caffeine improved performance in both trained and untrained participants. Exercise can also accompany a balanced diet in helping with weight loss and preventing obesity.
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Practical Considerations for Coffee Consumption
Coffee’s effects on health overall appear to be beneficial-in moderation. Research has consistently linked long-term coffee consumption to a lower risk of type 2 diabetes, heart disease, improved cognitive function and even lower mortality. But upping coffee intake simply to achieve these effects isn’t right for everyone. Drinking more than about 400 milligrams of caffeine per day might cause difficulty sleeping, more stress and some anxiety, he says.
Flavored lattes or frappes high in sugar and cream counteract some of the benefits that black coffee has on weight management. Sugar adds calories, and coffee is traditionally a calorie-free beverage. It is suggested to drink coffee with less sugar and cream instead.
The "Coffee Method" for Weight Loss
The "coffee method" for weight loss is rooted in the science of how caffeine affects metabolism, fat burning, and appetite. While it can provide a modest boost to your weight loss efforts, it is not a standalone solution. The most effective and sustainable way to lose weight is through a comprehensive approach that includes a healthy diet, regular exercise, and behavioral changes.
Maximizing the Health Benefits of Coffee
For those looking to maximize the health benefits of coffee, it’s best to consume organic and unfiltered coffee (like French press), since it retains more bioactive compounds like cafestol. It is also advised to avoid adding sugar or high-fat creamers, as the increased calories and unhealthy fats can negate the potential benefits and drink coffee in the morning or early afternoon to avoid sleep disturbances. If you like your coffee a little sweeter, natural sweeteners like stevia or small amounts of honey are preferable.