Nutrition Performance - Metabolic Advantage: A Calorie is Not a Calorie
“Four stages of acceptance: 1) This is worthless nonsense; 2) This is an interesting, but perverse, point of view; 3) This is true, but quite unimportant; 4) I always said so.”
Considerable attention has been given to the alarming rise in incidence of overweight and obesity in the U.S. The latest National Health and Nutrition Examination Survey (NHANES) shows that 64.5 percent of the U.S. population 20 years of age and older is now classified as overweight or obese! The first law of thermodynamics describes one of the most important principles related to obesity. The basic tenet states that energy cannot be created or destroyed but, instead, transform from one form to another. That human beings obeyed the first law of thermodynamics was demonstrated by Drs. Atwater and Benedict in 1903 and has been continually reaffirmed since then. In accord with the first law of thermodynamics, the energy equation dictates that body mass remains constant when caloric intake is equal caloric expenditure. Any chronic caloric imbalance on the energy output or input side of the equation changes body mass. Interestingly, published studies show that low-carbohydrate weight loss diets provide a metabolic advantage, a greater weight loss per calorie consumed compared to isocaloric high-carbohydrate diets.1 Unfortunately, these reports have been largely ignored (“don´t confuse me with the facts”), presumably because of apparent violation of thermodynamics (“a calorie is a calorie”). However, there is no such violation of thermodynamic laws. Energy utilization of different diets depends on the biochemical pathway taken; a metabolic analysis of the efficiency of different pathways reveals large differences. Thus, there is no theoretical contradiction in metabolic advantage and no theoretical barrier to accepting reports describing this effect.1
Don’t Confuse Me with the Facts According to a comprehensive literature review by Dr. Marjorie Freedman and colleagues at the U.S. Department of Agriculture published in 2001, “No scientific evidence exists to suggest that low-CHO [carbohydrate] ketogenic diets have a metabolic advantage over more conventional diets for weight loss. Studies consistently show that under conditions of negative energy balance, weight loss is a function of caloric intake, not diet composition”.2 However, in a recent study by Dr. B. Brehm and colleagues, 53 healthy, obese female volunteers were randomized for six months to either an ad libitum very-low-carbohydrate diet (20-60 grams/day) or a caloric-restricted diet with 30 percent of the total calories as fat, 55 percent as carbohydrate and 15 percent as protein.3 The women were examined at baseline, three months and six months. Results showed that despite ingesting approximately the same number of calories, women on the very-low-carbohydrate diets lost significantly more weight than did those on the caloric-restricted diet (8.5 vs. 3.9 kilograms; ~18.7 pounds vs.~8.6 pounds). In another study by Dr. F. Samaha and co-workers, 132 severely obese men and women with either diabetes or metabolic syndrome were assigned to either a low-carbohydrate or a caloric-restricted low-fat diet for six months.4 Seventy-nine subjects completed the study, which showed that those on the low-carbohydrate diet lost significantly more weight (5.8 vs. 1.9 kilograms; ~12.7 vs. ~4.2 pounds) and had greater improvements in triglycerides and improvements in insulin sensitivity than those on the low-fat diet. Finally, Dr. Penelope Greene and colleagues at the Harvard School of Public Health found that people eating an extra 300 calories a day on a low- carbohydrate diet diet lost a similar amount of weight during a 12-week study as those on a low-fat diet.5 Over the course of the study, they consumed an extra 25,000 calories. That should have added up to about seven pounds. But it did not. The study was unique because all the food was prepared at an upscale Italian restaurant, so research knew exactly what they ate. Not even Dr. Greene says this settles the case, but some found her findings fascinating. “A lot of our assumptions about a calorie is a calorie are being challenged,” said Dr. Marlene Scwartz of Yale. “As scientists, we need to be open-minded.” Others, though, found the data hard to swallow. “It doesn´t make sense, does it?” said Dr. Barbara Rolls of Pennsylvania State University. “It violates the laws of thermodynamics. No one has ever found any miraculous metabolic effects.” Hmmm… who is Dr. Rolls? Barbara J. Rolls, PhD, John Hopkins University School of Medicine (1992) (owned by none other than Mayor Michael Bloomberg of New York who was recently lambasted publicly for criticizing Dr. Atkins personally); professor of nutrition, Penn State University; consultant for Knoll Pharmaceuticals and has received research support from, among others, Knoll, P&G and ILSI. Co-authored (with James O. Hill) a 1998 report for ILSI on carbohydrates and weight management. Thus, it appears she is a carb industry shill.
What the Heck is Metabolic Advantage, Anyway? Recently, Drs. Richard D. Feinman and Eugene J. Fine published state-of-the-art paper on metabolic advantage and weight loss diets in a new scientific journal called Metabolic Syndrome and Related Disorders.1 In this review, they tabulated some of the experimental demonstrations of metabolic advantage. They showed that the apparent loss in energy in low-carbohydrate studies can be accounted for by differences in pathways and metabolic cycles and that this will appear as a thermogenic effect, as well as changes in body composition. Further, they proposed a plausible mechanism for metabolic advantage on low-carbohydrate diets. Finally, they provided a brief thermodynamic analysis and showed that, in fact, there is no barrier to accepting the published results. Thermogenesis (thermic effect of feeding) refers to heat generated in digestion and metabolism after feeding. Studies of macronutrient effects on thermogenesis show a substantially greater effect of protein compared to carbohydrate or fat. Thus, the energetically expensive protein turnover is a likely source of metabolic advantage on low-carbohydrate diets. Interestingly, there may also be a contribution due to the level of protein per se, independent of, or more likely, synergistic with, carbohydrate content. A recent study by Dr. Carol Johnston and co-workers found a 100 percent increase in thermogenesis with an 1,800 calorie low-fat diet with high protein compared to an isocaloric high-carbohydrate diet.6
Bottom Line According to Drs. Feinman and Fine, “The review presented here indicates that the reported metabolic advantage of low-carbohydrate diets has a plausible mechanism and is consistent with physical laws… Although the decline in body mass on weight loss diets is frequently proportional to caloric intake, a diet that offered the possibility of metabolic advantage would be of great practical value.” There are always some concerns about high-protein diets. For individuals with normal kidney and liver function, the risks are minimal and must be balanced against the real and established risk of continued obesity. The ridiculous notion that there is a single best diet for the whole population, as embodied, for example, in the pseudoscientific USDA Food Pyramid, is under attack in the popular and scientific press. Obviously, individual dieters must try different regimens to see which is the most effective and fits their individual lifestyles.
Guidelines for Dieting Bodybuilders and other Power-Strength Athletes • In my opinion, energy restriction is best achieved by a high-protein, moderate-carbohydrate, low-fat diet. • Protein intake should be about 1.5-2.5 grams per kilogram of body weight. The upper level of protein is recommended if energy restriction is substantial, as this may assist the maintenance of lean body mass and promote satiety. Eat low-fat/high-protein meat (e.g., fish, lean meat, skinless poultry) and low-fat/fat-free dairy products. • Increase consumption of non-starchy vegetables and low glycemic load fruits. Reduce intake of high-glycemic load carbohydrates with high-carbohydrate densities such as starches (e.g,, potatoes, pasta, rice) and grains. Consume moderate amounts of legumes. • Have most of the total fat intake be from nuts and oils that are rich in monounsaturated fats (e.g., olive oil). • Set a realistic rate of weight loss (i.e., 0.5 to 1.0 kilograms, or about one to two pounds, per week), including both short- and long-term goals. • Keeping a food record for a defined period (e.g., a week) is a useful task that allows you to appreciate exactly what you are eating. • A moderate energy restriction of 500 to 1,000 kilocalories per day is appropriate to producing a reasonable loss of body fat but still ensures adequate nutrient intake. • The meal plan for weight loss should not rely on skipping meals or enduring long periods without food intake. Rather, food intake should be spread over the day, particularly to allow for efficient refueling before and after training sessions and to avoid hunger (which generally precipitates overeating). • Use a broad-range, low-dose vitamin-mineral supplement if you will restrict energy intake for prolonged periods. • A significant part of weight loss and management may involve restructuring the environment that promotes overeating. Simple changes that can modify the eating environment: 1) prepare meals at home and carry bag lunches; 2) learn to estimate or measure portion sizes in restaurants; 3) learn to recognize fat content of menu items and dishes on buffet tables; and 4) modify the route to work to avoid a favorite food shop. • A myth that is circulating contends that in order to burn fat, you must exercise at a lower percentage of your maximal oxygen uptake (VO2max). This is certainly not the case. It is true that the percentage of energy obtained from fat is greater at lower exercise intensities (e.g., 50 percent VO2max) than at higher exercise intensities (e.g., 70 percent VO2max). However, at the higher energy intensity, you will derive a lower percentage of your energy output from fat, but the total energy expenditure will be greater, and you will still burn about the same amount of fat calories as you would exercising at the lower intensity, providing you are exercising for the same amount of time. If you want to burn calories to lose body fat, your objective should be to burn the greatest total calories possible within the time frame you have to exercise. • Exercise, particularly intense exercise, may be used to curb appetite on a short-term basis at an appropriate time. If you exercise before a meal, your food intake may be reduced considerably. Try it and see if it works for you. If you have the facilities available, a good half-hour exercise may be an effective substitute for a large lunch. • There are two medications approved for the long-term treatment of obesity. Sibutatramine is a norepinephrine and serotonin reuptake inhibitor that inhibits food intake centrally; orlistat is an inhibitor of pancreatic lipase functions. Although generally well tolerated, orlistat can give gastrointestinal symptoms such as abdominal cramps, soft stools and fecal urgency. If these symptoms were to occur during exercise, training disruptions could result. Phenylpropanolamine is approved for the short-term treatment of obesity (fewer than 12 weeks). Phenylpropanolamine is a central alpha-1 adrenergic stimulator that has no addictive potential and gives weight loss equivalent to prescription anorectic drugs during the first four weeks of treatment. Phenylpropanolamine has a remarkable safety record.8 Caffeine (200 milligrans) with ephedrine (20 milligrams) given three times a day is an approved obesity medication in Denmark. Weight loss is maximal at about four to six months on this combination, but body fat levels may continue to decrease through nine to 12 months, with an increase in lean body mass.9 The caffeine and ephedrine combination is also inexpensive. A month of treatment at wholesale prices runs less than $2.50, but since it is not covered by a patent, it is unlikely to be approved for the long-term treatment of obesity without government subsidy.8 Finally, a variety of drugs currently on the market for other conditions, but not approved by the FDA for obesity treatment, have been evaluated for their ability to induce weight loss. Metformin, cimetidine, diazoxide, bromocriptine, nicotine, bupropion and topiramate have produced modest weight loss.9 However, additional studies are needed to support these findings. Potential obesity drug candidates include cholecystokinin, corticotropin-releasing hormone, glucagons-like peptide 1, growth hormone and other growth factors, enterostatin, neurotensin, vasopressin, anorectin, ciliary neurotrophic factor, and bombesin, all of which potentially either inhibit food intake or reduce body weight in humans or animals.
