Weight Loss Ingredients – Which Ones Really Work?

Last updated December 23rd 2015

Whether or not a supplement is likely to aid weight loss is dependent on the ingredients that are used. Numerous ingredients are commonly added to supplements, but few of these are actually backed by clinical evidence.

Since the supplement market is unregulated, very few supplements have been clinically tested as whole products. As such, customers are forced to base their decision on clinical studies of the individual ingredients in a product.

Weight loss supplements are not classed as medications; instead, they are based on naturally derived herbal ingredients. Many of these ingredients are common to dietary supplements, but very few have been definitively proven to aid weight loss.

Here we will discuss a range of the most popular ingredients that are added to weight loss supplements. The efficacy and safety of each individual ingredient will be discussed using the clinical evidence available to date.

Fat Burning/Binding Ingredients

Fat binders are claimed to prevent the absorption of fat molecules into the body from the gastro-intestinal tract. Fat burning ingredients on the other hand are claimed to increase the speed at which fat molecules are broken down for energy. They are usually thought to achieve this by increasing the efficacy of the enzymes that are involved in the process. The majority of ingredients that are touted as fat burners are believed to cause thermogenesis – an increase in the internal body temperature. Some of the ingredients that are most commonly advertised as fat burners include green tea, raspberry ketones, and Garcinia cambogia.

Green Tea

Green tea is a very common ingredient to weight loss supplements. The ingredient is obtained from the steamed leaves of the Camellia sinensis plant. It is thought that the catechins in green tea, in particular EGCG (epigallocatechin gallate) have the potential to cause heightened fat burning. Studies that have investigated this claim have produced mixed results.

One study on 60 obese subjects found that, when taken for a period of 12 weeks, green tea could increase weight loss when compared to a placebo. The authors attributed this effect to increased fat burning and energy expenditure. Another study on 35 obese subjects produced similar results over eight weeks. Other trials however have shown green tea to be less effective. A study on 78 obese women found that after 12 weeks of treatment, green tea extract had no significant effect on body weight or BMI when compared to a placebo. A trial on 46 overweight women, published in 2005, also noted no significant difference in body weight or composition with the consumption of green tea compared to placebo when taken alongside a low-energy diet.

Raspberry Ketones

Raspberry ketones are chemicals that can be extracted naturally from raspberries or several other fruits, but are much more likely to have been made synthetically in a laboratory for use in weight loss supplements. The ingredient is very popular in diet pills, but precisely how raspberry ketones are supposed to aid weight loss is rarely described in detail. Nevertheless, they are commonly advertised as fat burners.

Clinical studies on raspberry ketones and weight loss are very few and have generally been of poor quality – utilising rats and mice as subjects rather than humans. As such, the results cannot be directly transferred to humans and so a definitive conclusion has yet to be been drawn. One study was published in 2005 and rested the effects of raspberry ketones on mice that were consuming a high-fat diet. The authors concluded that raspberry ketone could reduce the increases in fat that would usually be associated with a high-fat diet. In a 2012 study, rats were divided into five different groups with a normal or high-fat diet with varying levels of raspberry ketone supplementation. After eight weeks, the results suggested that raspberry ketone supplementation was beneficial for fat reduction.

Garcinia Cambogia

Garcinia cambogia is a small, green, pumpkin-like fruit that is native to Indonesia. The extract of this fruit contains a substance called hydroxycitric acid (HCA) that is believed to have the potential to increase the process of fat burning, although some sources claim that the ingredient works by fat binding, rather than fat burning. Once again, the precise mechanism employed by the ingredient is very rarely discussed on product websites.

This ingredient has been subject to only a few clinical studies, most of which have been of poor quality. A literature review reveals several reports of positive effects using rats, but only a handful of studies that have involved human subjects. One study using 60 human participants found that over eight weeks, subjects consuming Garcinia cambogia alongside a 2000kcal/day diet plus regular exercise lost a significant amount of fat. This study was however of poor quality, with no control group. A 2014 study of 43 human participants reported no significant effects on weight loss when compared to a placebo. Another study, this time using 135 volunteers, reported similar results, with no notable effects of Garcinia cambogia on body weight or fat mass.

Metabolism Boosting Ingredients

Metabolism boosting and fat burning are often said to go hand-in-hand, particularly for those ingredients that are believed to aid weight loss by causing thermogenesis. Thermogenesis is not only thought to improve the effectiveness of fat burning enzymes, but it is also said to cause a greater energy expenditure in general when the body is at rest. Most commonly, those ingredients that are described as metabolism boosters are stimulants, such as caffeine and synephrine; they might therefore provide the body with more energy as well as increase the metabolic rate.


Caffeine is perhaps the most common weight loss supplement ingredient to be described as a metabolism booster. The substance, which is found in everyday food products too, such as tea and coffee, causes a boost to the central nervous system. For this reason, it can cause increases in heart and respiration rate, and has been associated with an increase in energy expenditure (and so metabolic rate).

A study published in 2005 aimed to investigate the effects of caffeine on weight maintenance for three months following four weeks of a very-low-energy diet. Seventy-six overweight and obese participants were involved in the randomised trial. The results suggested that consuming high amounts of caffeine consumption could help to reduce body weight and fat mass when compared to consuming low amounts of caffeine. Another series of trials were performed to find out specifically what impact caffeine and coffee had on metabolic rate. Both normal-weight and obese subjects consuming 8mg/kg caffeine were seen to have a significantly increased metabolic rate after consumption compared to placebo; increased fat oxidation was also noted in normal-weight subjects.


Guarana extract is taken from the seeds of the guarana plant, native to the Amazon basin. The extract is most commonly used in herbal supplements to boost weight loss and athletic performance. This is mainly because the ingredient is high in caffeine and so should act as a central nervous system stimulant. In turn, it is also often advertised as a metabolism booster.

Guarana has not been well studied for its potential weight loss effects; most of the trials that have involved guarana have used a supplement that contains guarana alongside other ingredients. One trial, for example, looked at the effects of guarana and green tea when compared to a placebo. The results from 14 subjects suggested that 24-hour energy expenditure was significantly greater with the treatment than it was without. Guarana has also been shown to be effective for short-term weight loss when used alongside Ma-Huang (a banned substance) and other ingredients. A study using rats indicated that the weight loss effects of guarana are thanks to its caffeine content and that decaffeinated guarana will not have the same effect.

Bitter Orange

Bitter orange, also known by its scientific name: Citrus aurantium, is extracted from the skin of an orange-like fruit that can be found in many different regions of the world. The extract contains a chemical called synephrine that is thought to bring about weight loss benefits. It is a stimulant in nature, and so might have effects on the central nervous system. There is some concern regarding the safety of this ingredient.

A clinical review of the ingredient was published in 2012. Here, the authors identified a selection of studies (more than 20) that had been undertaken to determine the effects of synephrine in the short term. The data suggested that synephrine could increase energy expenditure and resting metabolic rate, resulting in some weight loss. Nevertheless, it is unclear whether or not bitter orange is safe for consumption, particularly in the long term. There have been reports of adverse cardiovascular events with its consumption; for example, a paper from 2004 documents the case of a patient suffering from a heart attack, potentially as a result of the ingredient.

Appetite Suppression Ingredients

Appetite suppressing ingredients can work in several different ways; they can typically be allocated to one of three different categories. Firstly, there are ingredients that supposedly suppress the appetite by physically filling up the stomach, making the user feel fuller for longer. Secondly, there are ingredients that are claimed to alter the concentrations of certain neurotransmitters in the brain that are involved in the signalling of satiety. Finally, some ingredients are said to help to control hunger cravings by helping to reduce spikes in blood glucose levels. Each of the ingredients discussed below is thought to work in one of these three ways.


Typically extracted from the root of the konjac plant, glucomannan is a fibrous ingredient that is said to swell up when in comes into contact with water. As such, when consumed as a supplement, glucomannan is understood to expand in the stomach, making the consumer feel full when they have not eaten. The European Food Safety Authority has reported a link between glucomannan intake and weight loss when users are following an energy-restricted diet.

A selection of clinical studies, though not all of them, have indicated that glucomannan might be effective for weight loss. A double-blind trial involving 20 obese participants who consumed either glucomannan or a placebo for eight weeks found that glucomannan could significantly reduce body weight, as well as improving cholesterol levels. A similar study, this time using 25 severely obese subjects, found that over a three-month period, glucomannan was able to significantly increase weight loss when compared to placebo. A meta-analysis of the available literature on the topic however, concluded after looking at the results of nine relevant studies, there is not evidence to suggest that glucomannan has a significant effect on weight loss.


Chromium is a trace mineral. The human body needs a very small amount of chromium to undertake a number of important bodily functions; most people do however consume plenty of chromium for these purposes from their usual diet. It is thought that supplementing with chromium might help to suppress the appetite by improved the control of blood glucose levels after a meal. Chromium has also been associated with improving body composition in the past.

A study of 122 participants was performed to test the effects of chromium supplementation on body weight and associated factors. The subjects took chromium or a placebo for 90 days. Results indicated that those in the chromium group lost more weight and more fat mass. A second trial however reported no significant impacts of chromium on body fat reduction. This study was double blind, involved 95 Navy personnel and continued for 16 weeks. Studies looking specifically at appetite suppression have also produced mixed results. Some trials have suggested that chromium supplementation can cause reduced food intake, hunger levels, and fat cravings when compared to placebo.


Capsicum, also sometimes called capsaicin, cayenne pepper or red pepper on ingredients lists, is extracted from members of the Capsicum chilli family. The chemical is believed to have a selection of health benefits; in terms of weight loss, it is thought to have the potential to increase the metabolism and suppress the appetite.

A few studies have considered the potential benefits of capsicum for weight loss. A 2005 trial investigated the impacts of capsaicin, the active component of capsicum, on satiety and food intake. Twenty-four male and female participants were involved in the trial, and their food intake was recorded for 16 hours four times over two days. Before each meal, subjects were given red pepper or placebo. It was concluded that capsaicin could boost satiety and reduce energy and fat intake in the short term. Another study employed similar methods. For this trial, 30 subjects were given lunch either with or without capsaicin in a crossover design and energy intake and thermogenesis was monitored. The results were not suggestive of a significant effect of capsaicin on satiety or energy expenditure.

Carbohydrate Blocking Ingredients

Compared to fat burners, appetite suppressants and metabolism boosters, there are very few ingredients that are claimed to work as carbohydrate blockers. The most common of these is white kidney bean extract. Carbohydrates are large, complex molecules and when they are consumed in the diet, they need to be broken down into their smaller sugar components before the body can absorb them. Carbohydrate blocking ingredients are said to attach to the enzymes that undergo this process, thereby preventing a small proportion of the molecules from being broken down and preventing them from being absorbed by the body. Some of the carbohydrates consumed should, in theory, be passed through the digestive tract without being absorbed through the lining of the intestine.

White Kidney Bean

White kidney bean extract is the most common ingredient that is claimed to work as a carbohydrate blocker. The ingredient is also sometimes listed by its official name – Phaseolus vulgaris. Phaseolus vulgaris is considered by the FDA to be generally safe when used in foodstuffs. Besides for the treatment of obesity, white kidney bean extract has also been used in traditional medicine to reduce cholesterol and treat conditions such as lung cancer and urinary tract infections.

Phaseolus vulgaris has been the subject of a number of clinical trials that have investigated its potential weight loss effects. A study published in 2007 examined the impacts of white kidney bean extract on body composition. Sixty slightly overweight subjects were given either 445mg Phaseolus vulgaris extract or a placebo daily before a high-carb meal for 30 days. The results indicated that the extract could significantly reduce body weight and fat mass whilst helping to maintain lean body mass when compared to placebo. Another paper provides a review of the effects of a specific white kidney bean product. The authors noted that the substance could improve weight loss at daily doses of 500 to 3000mg and that it might also improve blood glucose levels.

Protein Ingredients

Protein shakes are becoming increasingly popular in the supplement market and are regularly advertised for their potential weight loss benefits. Most protein shakes are based on one form of protein, such as whey, soy or casein, though some will use a mixture of protein sources combined with other ingredients, such as green tea extract and caffeine. The two main areas of weight loss associated with protein are appetite suppression and fat burning. Protein shakes are not always thought to directly burn fat via thermogenesis, but they might be claimed to improve exercise performance and body composition by helping to maintain muscle mass at the expense of fat.

Whey Protein

Whey protein is a form of protein that is created as a by-product in the production of cheese. The ingredient is therefore described as a dairy substance and is perhaps the most popular source of protein for protein shakes. Whey protein is a good source of amino acids and is thought to be fast acting. Of all of the different forms of protein used in shakes, whey protein is probably the most extensively studied for its potential weight loss and muscle building benefits.

A 2006 study investigated the impacts of whey protein supplementation on strength and body composition when compared to casein protein using 13 males, recreational bodybuilders as subjects. By the end of a 10 week training plus treatment period, it was found that those in the whey protein group gained significantly more lean mass and lost more fat mass than those in the casein protein. Another study looked at the effects of whey protein, soy protein and a carbohydrate control on 90 free-living overweight and obese subjects. After 23 weeks, the body weight and fat mass of the whey protein group was significantly lower than the carbohydrate group.

Soy Protein

Soy protein is extracted from the soybean; the beans can be eaten as food and are said to contain all of the essential amino acids but no cholesterol. As soy protein is made from a plant source, it is popular amongst vegetarians and those who are lactose intolerant. Similarly to whey protein, soy protein is thought to be beneficial for muscle gain, fat loss, and appetite suppression.

Soy protein has also been subject to clinical study, although not to such a great extent as whey protein. One placebo-controlled study, for example, looked at the effects of a diet high in soy protein on body composition, amongst other factors, using 90 pre-obese and obese subjects. The trial continued for six months, at which point measurements suggested that soy protein could help to improve body composition, preserving muscle mass whilst aiding the loss of fat. A review study agreed with these results. After reviewing the relevant literature, the authors of this paper reported that soy protein could have a positive role in obesity by reducing body weight and fat mass as well as reducing cholesterol and triglyceride levels.

Casein Protein

Like whey protein, casein protein is extracted from cows’ milk. Unlike whey protein however, casein is considered to be a slow-acting protein and so is often claimed to be useful for recovery from exercise, rather than being used as a pre-exercise drink. It has also been touted as an appetite suppressant in the past.

There are fewer clinical trials on casein than there are on whey protein or soy protein. Some studies have compared the three proteins, listing casein as the least effective for muscle synthesis; casein is however understood to be more beneficial for appetite suppression. A study from 2010 found in a comparison of the three main types of protein that casein protein provided the best results for satiety, whilst soy protein had a significant effect on thermogenesis and whey had a significant effect on respiratory quotient. A second study produced similar results, indicating that casein protein (and pea protein) were better for satiety than whey or egg proteins.

Shutterstock Shake Bought


When choosing a weight loss supplement, it is important that you look into the ingredients carefully. Very few supplements have been clinically tested as whole products, so it is useful to see whether or not the ingredients have shown any potential in clinical trials. The majority of ingredients in weight loss supplements have not been definitively proven to aid weight loss; nevertheless, some have been shown to have a very slight effect on weight loss. It is important to note that some of the more popular ingredients in supplements, such as raspberry ketones and Garcinia cambogia, are backed by very little evidence. Clinical studies also offer some insight regarding the safety of weight loss ingredients.