Thermogenics Turn Up the Heat in weight Loss

Managing weight is a fact of life for most adults; the scale goes up and down, and we promise we’ll cut back on those desserts or get back to the gym. At this point, the United States is facing an epidemic of overweight and obesity, with more than two-thirds of Americans weighing more than is considered optimal for their height.

Interestingly, while the federal government has increasingly touted exercise as one of the critical steps in losing and managing weight—even adding it to the federal dietary guidelines—a cover article in Time magazine at the height of the 2009 summer swimsuit season questioned the conventional wisdom. The theory put forth in “Why Exercise Won’t Make You Thin” is exercise stimulates appetite instead of suppressing it and feeds into the mental idea of “earning” extra calorie intake. And while the author noted muscle does burn more calories than fat, he added the difference in calorie burning is negligible.

One reason for the inefficiency in fat burning? Humans generally lack great quantities of “brown fat,” which is better at turning nutrients into energy. Researchers at Boston’s Joslin Diabetes Center recently published an analysis of amount of brown adipose tissue (BAT) and its influence on thermogenesis, mediated by the expression of uncoupling protein 1 (UCP1), in almost 1,800 adults.1 They found women generally had a greater mass of functionally active BAT, and reported an inverse correlation between BAT levels and body mass index (BMI).

The question may be how to stimulate BAT activity and thermogenesis in adults. Fortunately, studies are increasingly pointing to the ability of many nutritional ingredients, from macronutrients to botanicals, to upregulate the body’s process of thermogenesis—increasing the metabolic rate to burn energy.

Every individual has a basal metabolic rate (BMR) linked to the amount of energy needed to maintain basic life functions; this generally slows as the body ages and muscle mass and activity level decline. Metabolic energy needs are also influenced by physical activity (basic and more strenuous activity, such as exercise) and digestion. In fact, the metabolic rate increases immediately after eating, as the body works to transport, metabolize and absorb nutrients.

Protein has been shown to significantly increase diet-induced thermogenesis. A review out of Maastricht University, Netherlands, noted sustaining protein intake can affect metabolic targets during weight loss, particularly during calorie restriction, helping to sustain energy expenditure and spare lean body mass.2 Additionally, moderately elevated protein intake while reducing overall calories appears to increase thermogenesis, influencing satiety, while maintaining lean muscle mass, further improving the metabolic profile.3 In one recent study, researchers out of Purdue University, West Lafayette, IN, reported women (n=38) consuming a high-protein, energy-deficit diet had greater satiety and fat oxidation compared to a normal protein diet.4

Some studies suggest dairy protein in particular may exert positive effects on thermogenesis and accelerated fat loss, supported by higher calcium levels inhibiting lipogenesis and bioavailable protein affecting satiety and lipolysis.5 In one double blind, randomized study at the Minnesota Applied Research Center, subjects (n=106) reduced their caloric intake by 500 calories per day and consumed a specialized whey fraction (as Prolibra™, from Glanbia) or an isocaloric ready-to-mix beverage 20 minutes before breakfast and dinner.6 The Prolibra group lost significantly more body fat compared to control subject, with a greater preservation of lean muscle.

It may be the amino acids found in protein exert a particular effect on the body’s thermogenic pathways. Italian researchers reported providing an amino acid-infused solution to adults increased protein synthesis and energy expenditure, with the thermic effect not dependent on the dosage of amino acids.7 L-leucine specifically may stimulate protein synthesis in muscle cells and promote retention of lean muscle mass during calorie reduction.8 It also appears to regulate the oxidative use of glucose by skeletal muscle, sparing protein during energy restriction.9

The amino acid L-carnitine may also exhibit some thermogenic properties. A recent French study found providing aged rats with 30 mg/kg body weight of L-carnitine (as L-Carnipure™, from Lonza) for 12 weeks restored L-carnitine levels in muscle cells and induced positive changes in body composition including a decrease in abdominal fat mass without any change in food intake.10 A previous human trial examined the impact of L-carnitine supplementation on fat oxidation, body composition and weight development in 12 slightly overweight adults.
By Heather Granato