Thermogenic Fat Burners for Weight Loss

America is obsessed with eating and it shows. Globally, there are more than 1 billion overweight adults; 300 million of those adults are obese, according to the World Health Organization (WHO). WebMD defines obesity as having so much body fat that your health is at risk. Consumers with a body mass index (BMI), a statistical measure of weight scaled according to height, of 30 or higher are considered obese. Along with diet, a decrease in physical activity is also a contributing factor to obesity; more than half of U.S. adults do not get enough physical activity to provide health benefits and 24 percent are not active at all during their leisure time, according to the Centers for Disease Control and Prevention (CDC).

With that much fat lying around, it’s no wonder weight loss is on the forefront of everyone’s mind. Diet choices are endless, with Weight Watchers, Jenny Craig, Atkins, Mediterranean, the Cabbage Soup diet and many more.

Burning fat has become a popular approach to weight loss, especially in dietary supplement category. Many consumers are using thermogenic (fat burning) dietary supplements along with diet and exercise to increase weight loss. Thermogenic dietary supplements are used to stimulate the body’s burning of fat; they boost the metabolic rate in the adipose tissue, which generates heat, hence the name thermogenics. Adipose tissue’s primary role is to store energy in the form of fat, but it also cushions and insulates the body. Brown adipose tissue (BAT) and white adipose tissue (WAT) are the two types of adipose tissue. The primary purpose of BAT is to generate body heat; however, most adults don’t have much BAT.

Basic Ingredients

Diet-induced thermogenesis is a popular way to improve fat burning and weight loss. Protein has recently received a lot of attention with new research showing its satiating ability as well as its thermogenic fat burning characteristics. The Royal Veterinary and Agricultural University, Copenhagen, Denmark, conducted a study comparing the effects of pork-meat protein, soy protein and carbohydrates on a 24-hour energy expenditure with 12 young, healthy, overweight and mildly obese nonsmoking men in a randomized, single blind, three-way crossover study lasting four days.¹ The study concluded substituting 17 to 18 percent of the carbohydrate energy with pork meat or soy protein produced 3 percent higher 24-hour energy expenditure. The animal protein in the pork meat produced 2 percent higher 24-hour energy expenditure than the soy protein.

In a separate study out of Mexico, researchers found when soy protein diets were consumed with a 5 percent fat or 25 percent high-fat diet, less weight was gained than when a casein protein diet was consumed, partly because of an increase in the thermogenic fat burning capacity mediated by uncoupling protein 1 (UCP-1).² The study suggested the type of protein consumed and the presence of fat in the diet modulate lipid metabolism in adipose tissue and liver.

Another study looked for differences in thermogenesis and macronutrient oxidation between lean and obese women.³ Fifteen lean and 15 obese women were studied on two occasions, one week apart. In one visit, they consumed a protein-rich meal; in the other visit, a fat-rich meal. The two meals were isocaloric, of equal volume and given in random order. Thermogenesis was not significantly different between lean and obese subjects after eating the protein-rich or the fat-rich meal; however it was significantly higher, by almost three-fold, after consumption of the protein-rich meal in comparison with the fat-rich meal in both study groups.

A recent study at Maastricht University, Netherlands, showed greater larger thermogenesis and fat burning after consuming protein versus carbohydrate may be related to the glucagon response that is induced by protein, but not by carbohydrates; protein-induced thermogenesis and glucagon response are not influenced by a carbohydrate pre- or post load.⁴ The researchers also reported protein ingestion can fully prevent the plasma glucose increase associated with a carbohydrate when carbohydrates are ingested after proteins.

A study published in Metabolism tested the effect of L-carnitine, a naturally occurring amino acid, on fat oxidation, protein turnover, body composition and weight development in slightly overweight subjects.⁵ L-carnitine created a significant increase in 13C-fat oxidation without protein catabolism; protein synthesis and breakdown rates remained unchanged.

Another basic ingredient used to stimulate thermogenesis is water. A 2007 study from the Franz Volhard Clinical Research Center in Berlin repeated previous studies that showed drinking 500 ml of water induces thermogenesis in normal-weight men and women.⁶ Researchers used overweight or obese but otherwise healthy subjects and compared the effects of 500 ml of isoosmotic saline or 50 ml of water. The study showed only 500 ml of water increased energy expenditure by 24 percent over a course of 60 minutes after ingestion, whereas isoosmotic saline and 50 ml water had no effect.

A more commonly known thermogenic fat burner that can really spice things up is capsicum frutescens or chili pepper. A study in 2003 evaluated 10 Thai women and their glucose response after a glucose drink and their metabolic rate with and without 5 g of fresh chili pepper.⁷ Thirty minutes after ingesting fresh chili pepper, the plasma glucose was 20.6 percent lower than the plasma glucose after the glucose drink without chili pepper. The chili powder increased the metabolic rate above resting metabolic rate (RMR). There was also an immediate increase of 20 percent in the metabolic rate within a few minutes of taking the chili pepper.

A different study found a combination of tyrosine, an amino acid; capsaicin, the active component of chili pepper; catechines, polyphenolic antioxidant plant metabolites found in tea; and caffeine increased four-hour thermogenesis by 90 kJ more than a placebo; the effect was maintained after eight weeks and accompanied by a slight reduction in fat mass.⁸

Conjugated linoleic acid (CLA), an unsaturated omega-6 fatty acid mainly found in dairy products and meat, has been shown to reduce body fat and prevent weight gain. The International Journal of Obesity published a study in 2001 that found a four-week supplementation of CLA (as Tonalin® CLA, from Cognis Nutrition and Health) in obese men with metabolic syndrome may decrease abdominal fat, without simultaneous effects on overall obesity or other cardiovascular risk factors.⁹ The researchers added due to the limited sample size, the effects of CLA in abdominal obesity need to be further investigated in larger trials with longer duration. A Scandinavian study demonstrated a significantly higher reduction in body fat mass for groups who ingested CLA (P=0.03), compared to the placebo group; however, there was no effect on body fat mass with CLA doses higher than 3.4 g/d.¹⁰

Interestingly, one French study showed CLA supplementation did not affect adipose weight or the components of energy expenditure despite a theoretically higher capacity of red muscle to burn fat; but it did prevent the body from increasing levels of triglycerides, a type of fat.¹¹ However, a 2007 study reported supplementation with 4 g/d of 78 percent active CLA isomers (as Tonalin) increased fat utilization, fat burning and energy expenditure during sleep in healthy adults.¹²

Stress can also induce thermogenesis, according to an Australian study indicating psychological stress causes activation of 5-HT2A receptors, a member of the serotonin receptor family, in neural pathways that control thermogenesis in the BAT and facilitate the narrowing of blood vessels in the skin.¹³

Botanical Ingredients

Botanicals also contribute to thermogenesis. Bitter orange (Citrus aurantium) was one of the high-profile ingredients formulators turned to when ephedra (Ma huang) was taken off the market. Studies have supported its efficacy and safety. One double blind, placebo-controlled study at Greenwich Hospital in Connecticut involved subjects given Citrus aurantium extract (as Advantra Z®, from Nutratech), caffeine and St. John’s wort while on a strict diet and exercise plan.¹⁴ At the end of six weeks, subjects in the treatment group lost significantly more body weight and fat than those in the placebo or control group. There were no significant changes in blood pressure, heart rate, electrocardiographic findings, serum chemistrics or urinalysis, suggesting the combination of Citrus aurantium extract, caffeine and St. John’s wort is safe and effective when combined with mild caloric restriction and exercise for promoting both body weight and fat loss in healthy overweight adults.

A Canadian study conducted in 2005 stated the thermogenic effect of food in men, when given Citrus aurantium as a supplement, was much higher than in women; however, when both male and female subjects were administered Citrus aurantium in their meal, it increased the thermic effect of food of only women to values no longer different from men.¹⁵Citrus aurantium had no effect on blood pressure and pulse rate but it increased epinephrine excretion by 2.4 fold.

In an unpublished study supported by Nutratech Inc. at the University of Colorado, Colorado Springs, researchers found ingestion of Advantra Z in an herbal blend increased the RMR without affecting heart rate and blood pressure.

Green tea and green bean coffee extract are popular mainly for their high antioxidant content; however, they also appear to play a role in fat burning. A Japanese study conducted in 2006 found green bean coffee extract “is possibly effective against weight gain and fat accumulation by inhibition of fat absorption and activation of fat metabolism in the liver.”¹⁶

Green tea, meanwhile, was found in a study out of the University of Geneva to significantly increase 24-hour energy expenditure and significantly decrease 24-hour respiratory quotient without any change in urinary nitrogen.¹⁷ The researchers concluded green tea extract has thermogenic fat burning properties and promotes fat oxidation beyond that explained by its caffeine content per se and it may play a role in the control of body composition through sympathetic activation of thermogenesis, fat oxidation or both.

Another study involved 14 subjects given a placebo or a capsule of 200 mg of caffeine and epigallocatechin-3-gallate (EGCG), a catechin found in green tea, three times daily 30 minutes before meals.¹⁸ The results showed a significant increase in 24-hour energy expenditure with all EGCG-caffeine mixtures compared with the placebo. There was no effect observed for lipid oxidation with the EGCG-caffeine mixture.

Researchers at the University of Fribourg in Switzerland speculated on a mechanism of action, reporting green tea extract stimulates BAT thermogenesis beyond what would be expected solely from its caffeine content, and its thermogenic fat burning properties could be primarily from an interaction between its high content in catechin-polyphenols and caffeine with sympathetically released noradrenaline.¹⁹

Other herbal supplements have also shown promise for thermogenic activity. The Journal of Human Nutrition and Dietetics published a study examining the effects of an herbal mixture of yerba maté, damiana and guarana on gastric emptying and weight loss and maintenance.²⁰ The herbal mixture significantly delayed gastric emptying, reduced the time to perceived gastric fullness and induced significant weight loss over 45 days.

Garcinia cambogia is a South Asian fruit that contains hydroxycitric acid (HCA). HCA has been shown to significantly suppress food intake and body weight regain; its effects were not impacted by adding CLA or guar gum.²¹ Another study published in Gene Expression showed a patented HCA ingredient (as Super CitriMax®, from InterHealth Nutraceuticals) significantly restricted body weight growth.²² The response was associated with lowered abdominal fat leptin, a hormone indicating degree of hunger, while plasma leptin levels remained unaffected.

And a study at Georgetown University Medical Center, Washington, demonstrated Super CitriMax and, to a greater degree, the combination of Super CitriMax, ChromeMate® niacin-bound chromium and Gymnema sylvestra extract could serve as safe weight management supplements.²³ Sixty moderately obese subjects were randomly assigned to receive 4,667 mg/d of Super CitriMax or a combination Super CitriMax and 400 mcg of ChromeMate and 400 mg of Gymnema sylvestra extract or a placebo. After eight weeks, body weight and BMI decreased by 5 to 6 percent in both the Super CitriMax group and the Super CitriMax, ChromeMate and Gymnema sylvestra group.

Licorice flavonoid oil is a newer thermogenic botanical compound shown to suppress fat accumulation. In 2004, a study reported that licorice hydrophobic flavonoids have abdominal fat-lowering and hypoglycemic effects.²⁴

Another hot new ingredient in the thermogenic fat-burning arena is fucoxanthin, a carotenoid found in edible seaweed. A Japanese study reported fucoxanthin helps reduce abdominal WAT weights in rats; supplementation also upregulates the expression of mitochondrial uncoupling protein 1 in WAT.²⁵ Another study involved administration of fucoxanthin and fish oil to mice; the results showed a greater reduction in weight gain of WAT when both fucoxanthin and fish oil were combined versus just fucoxanthin.²⁶

The International Journal of Molecular Medicine published a study that showed fucoxanthinol, fucoxanthin’s metabolite, exhibited greater suppressive effects on lipid accumulation and decreased glycerol-3-phosphate dehydrogenase activity than sole fucoxanthin.²⁷

Specialty Ingredients

Specialty ingredients, such as 3-acetyl-7-oxo-dehydroepiandrosterone, better known as 7-oxo-DHEA, also weigh heavy in the thermogenic area. In one recent study, 30 obese subjects took 7-oxo-DHEA (as 7-Keto® from Humanetics Corp.) or a placebo twice a day for eight weeks.²⁸ The rate of change in body fat per four-week interval in the 7-Keto group was 3.1 times that in the placebo group. The study showed that 7-Keto combined with exercise and a reduced calorie diet, reduces more body weight and fat than without the supplement.

Along the same lines, another recent study found 7-Keto in combination with calcium citrate, green tea extract, ascorbic acid, chromium nicotinate and cholecalciferol (HUM5007) increased RMR and thermogenesis above basal levels with the possibility of benefiting obese individuals with impaired energy expenditure.²⁹ And a randomized, double blind, placebo-controlled trial in 2005 found overweight subjects who supplemented with a formula containing 7-oxo-DHEA, L-tyrosine, asparagus root extract, choline bitartrate, inositol, copper gluconate, manganese, and potassium iodide (as 7-Keto Naturalean™), in addition to diet and exercise, had greater weight loss than just diet and exercise.³⁰

Another option is a thermogenic drink. A 2008 study showed a thermogenic drink (as Celsius™ from Celcius Inc.) significantly increased the resting energy expenditure, free-fatty acid and glycerol appearance concluding “it may promote weight loss and improve body composition.”³¹ Another study gave 20 healthy men and women 12-oz. of Celsius™, and on a separate day, gave the same subjects 12-oz. of Diet Coke®.³² Testing indicated that the metabolic rate increased by 13.8 percent after one hour, 14.4 percent after two hours and 8.5 percent after three hours of ingesting Celsius™. On the contrary, statistically insignificant increases in metabolic rate were noted after Diet Coke® was ingested.

Shedding pounds is not an easy thing to do, but with the help of natural supplements encouraging thermogenesis, it can help take some “weight” off.

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Editor's Note: Interested in learning more about the weight management category? Check out the free INSIDER Webinar, "A Real World Look at Weight Management" online.

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