Green coffee bean extract for weight loss is gaining in popularity as research evidence continues to support its use in boosting metabolism and stimulating fat burning. While green coffee bean extract is often dismissed as simply a source of caffeine, its weight loss potential is boosted by the presence of powerful, antioxidant polyphenols known as chlorogenic acids, or CGAs for short. These CGAs enhance fat burning through interactions with genes present in both the cell nucleus and your cells energy factories, or mitochondria.
Green coffee bean extract
Coffee beans are the seed of a vigorous shrub, of which two main species produce arabica coffee and robusta coffee. These shrubs produce small, cherry-like fruits which contain either one or two seeds. After harvesting and sun-drying, these seeds are used to produce green coffee bean extract.
Green coffee beans contain over 1000 biologically active compounds, of which caffeine and a type of polyphenol known as chlorogenic acids (CGA) are the most studied for their weight loss benefits.
Green robusta beans contain almost twice as much caffeine (2.7%) as arabica beans (1.5%) and also have a higher concentration of chlorogenic acids – typically 10% of their dry weight compared with 5% for Arabica coffee.
Green coffee bean extract and caffeine
The caffeine found in green coffee beans stimulates metabolism to increase fat breakdown, partly by raising circulating levels of adrenaline hormone, which releases free fatty acids from fat stores.
In one study, a single dose of 100 mg caffeine increased the resting metabolic rate of both lean and obese volunteers by 3% to 4% over 150 minutes, as well as increasing the amount of heat they generated (diet-induced thermogenesis). Repeated caffeine doses of 100 mg every 2 hours for 12 hours increased their energy expenditure by between 8% and 11% during that period. The overall result was that the lean individuals burned an additional 150 kcals energy, while the obese volunteers burned an additional 79kcals.
In another study, 12 healthy males drank 150 ml decaffeinated coffee (containing CGAs), with or without 200mg added caffeine. Their resting metabolic rate, skin and core body temperatures were monitored over the following 3 hours. Caffeine ingestion had an immediate, significant effect in boosting their metabolic rate by an average of 7% which was sustained for at least the following testing period of 3 hours. Internal and skin temperature increased with both the decaffeinated and caffeinated coffee, but was greater after consuming caffeine.
Decaffeinated coffee bean extracts are available if you prefer to avoid the stimulating effect of caffeine which can keep you awake at night, and will still boost weight loss due to the presence of chlorogenic acids (CGA).
Green coffee bean extract and CGA
Normal roasted coffee beans contain little, if any CGA, as roasting destroys coffee bean chlorogenic acids so their level halves within 12 minutes and disappears after 20 minutes. For optimum weight loss benefits, over and above the effects of caffeine, it’s therefore important to use green coffee bean extract.
Chlorogenic acids are powerful activators of a gene (SIRT1) that boosts metabolism so you burn more fat, and convert more energy to heat, especially in brown fat cells, to speed weight loss. This effect can raise your metabolic rate by as much as 10% for two to three hours.
The CGAs in coffee also slow glucose absorption, and regulate the release of gut hormones which reduce hunger. If you have difficulty losing weight, drinking coffee and/or taking green coffee extracts may help.
Green coffee bean extract for weight loss
Initially, green coffee bean extract gained a bad reputation when one manufacturer-funded study showed extraordinary reductions in body weight of 8kg in 22 weeks. This study was retracted following allegations of data falsification. Leaving that study aside, most of the research investigating the effects of coffee on metabolism and weight loss are small, but show promising results.
In one study, 30 overweight volunteers drank instant coffee enriched with 200mg of chlorogenic acid (green coffee bean extract) for 12 weeks and lost significantly more weight than those drinking normal instant coffee. Average weight loss in those drinking the chlorogenic acid enriched coffee was 5.4kg compared with 1.7 kg in those drinking normal coffee – an increased weight loss of 3.7kg over three months.
In a similar study, those who consumed 100mg green coffee bean extract, or placebo, twice a day with meals, for 60 days, while following a low-calorie diet. At the end of the two months, they lost an average of 4.97kg in weight more than those taking placebo. Their ratio of muscle mass to fat mass also increased.
In another study, 33 volunteers drank freshly brewed arabica coffee enriched with green coffee bean extract (250mls, three times a day) for 4 weeks. They lost 0.68kg fat during the month, despite making no other changes in their normal dietary or lifestyle habits. This effect was attributed to the increased metabolic rate associated with caffeine and green bean extract chlorogenic acids, and a suppression of appetite which significantly reduced energy intake.
The results from three clinical trials, involving 142 people, suggest that taking 180mg to 200mg green coffee bean extract while following a weight loss diet can boost fat loss by an average of 2.47 kg (one study lasted 4 weeks, producing a weight loss of 1.35kg more than placebo, two studies lasted for 12 weeks and produced weight losses of 5.4kg and 4.97kg more than placebo).
The most recent clinical trial, involving 64 obese women, compared the effects of taking 400mg green coffee bean extract per day for 8 weeks, against placebo, while following a low-calorie diet. Those taking the green coffee bean extracts lost more weight (4.84kg versus 2.62kg), fat mass, and their waist-to-hip ratio improved more than in the placebo group. The researchers concluded that green coffee bean extract combined with an energy-restricted diet is an inexpensive method for improved weight control.
Green coffee beans and appetite
Green coffee bean extract may also suppress hunger. A study involving 10 men and 10 women investigated the effects of taking a 300mg dose of caffeine half an hour before they were offered an eat-all-you-want meal. In men, pre-loading with caffeine reduced the amount eaten at the meal by 21.7% compared to placebo (816 kcals versus 1043 kcals) but in women the effect was not statistically significant (603kcals vs 625 kcals).
When 33 volunteers had 200 ml of coffee providing either 3mg caffeine per kg body weight, or twice as much, those that were overweight or obese ate significantly less at a subsequent buffet meal, than when they drank water with breakfast. The higher dose of caffeine produced the greatest effect.
Another study found that decaffeinated coffee also suppressed appetite which suggests the CGAs also have an effect.
Green coffee bean extract and diabetes
CGA polyphenols reduce glucose absorption in the small intestine, improve insulin resistance and reduce the release of glucose from the liver. These improvements in glucose regulation, together with effects on the release of gut hormones involved in satiety, help to suppress hunger and may reduce the risk of type 2 diabetes.
In one study, 30 overweight volunteers drank instant coffee enriched with chlorogenic acid (green coffee bean extract) for 12 weeks and as well as losing significantly more weight than those drinking normal instant coffee, their glucose absorption was reduced by 6.9%.
Green coffee bean extract and cholesterol
In the weight loss trial involving 64 obese women, taking 400mg green coffee bean extract per day for 8 weeks while following a low-calorie diet lowered total cholesterol and LDL-cholesterol significantly more than placebo.
Green coffee bean extract supplements
Although studies have involved small numbers of people, they suggest that adding green coffee extracts to a sensible diet and exercise regime could provide additional help if you are struggling to lose weight.
Select good quality brands made to a pharmaceutical standard known as GMP to ensure they are checked at every stage of processing for purity, and provide a consistent dose. Some unregulated green coffee brands were withdrawn from teh market when they were found to contain a prescription-only drug, sibutramine, which is no longer used medically to assist weight loss due to side effects.
Green coffee bean extract side effects
Green coffee bean extracts contain caffeine, which can increase blood pressure in some people. The chlorogenic acids have the opposite effect, however, by improving blood vessel elasticity. As a result, taking green coffee bean extract is associated with a significant reduction in blood pressure in people with mild hypertension.
Coffee itself also appears to have beneficial effects against heart and circulatory disease.
Although none of the clinical trials reported any serious side effects, one person withdrew from a study because of headache (possibly related to the caffeine) while another withdrew due to a urinary tract infection (probably not related to the extracts).
If you are taking any prescribed medication, it’s always wise to seek advice from your doctor or a pharmacist before taking any supplements.