Nutrition Performance - Latest Findings on High-Protein/Low-Carb Diets
“I do not feel this topic [low-carb diets] should be studied at all.”
Dr. David Katz
Yale University
Thermodynamics and the High-Protein/Low-Carb Diet
The first law of thermodynamics describes one of the most important principles related to bodyweight. The basic tenet states that energy cannot be created or destroyed, but, instead, transform from one form to another without being depleted. In accord with the first law of thermodynamics, the energy balance equation dictates that body mass remains constant when caloric intake equals caloric expenditure. Any chronic imbalance on the energy output or input side of equation changes body mass.
Thus, the key to weight loss/fat loss is simply the daily consumption of fever calories than are expended. However, it’s easier to moderate caloric intake in a diet that has adequate quantities of protein because of superior satiety compared with a high-carbohydrate diet. Further, higher protein intake increases dietary thermogenesis. Dietary thermogenesis consists of two components. One component is called obligatory thermogenesis and it results from the energy required for digesting, absorbing and assimilating food nutrients.
The second component, called facultative thermogenesis, relates to the activation of the sympathetic nervous system and its stimulating affect on metabolic rate. Because of protein´s relatively high thermic effect, fewer calories ultimately become available to the body compared with a meal of similar caloric value consisting mainly of fat or carbohydrate.
I just read with great interest the recent paper entitled “Is a calorie a calorie?” by Drs. Andrea Buchholz and Dale Schoeller in the American Journal of Clinical Nutrition discussing thermodynamics and weight loss diets.1 The authors concluded that high-protein/low-carb diets produced about 2.5 kilograms (5.5 pounds) greater weight loss after 12 weeks of treatment. According to the authors, neither macronutrient-specific differences in the availability of dietary energy nor changes in energy expenditure could explain these differences in weight loss.
However, they ignored the fact that energy utilization of different diets depends on the biochemical pathways taken.2
For example, a low-carbohydrate diet dramatically increases gluconeogenesis (the formation of glucose from noncarbohydrate molecules such as amino acids) compared with a high-carbohydrate diet. Obviously, gluconeogenesis is an energy-consuming process.3 Further, the energy-dependent processes of maintaining the turnover of proteins, including synthesis, folding, targeting, regulatory processes and protein breakdown, have an overall cost to body energy homeostasis that is significantly higher than previously appreciated.4 Thus, it’s not surprising that high-protein/low-carb diets are so effective.
Manipulation of Low-Carb Data
A systemic review published in the Journal of the American Medical Association concluded that “weight loss while using low-carbohydrate diets was principally associated with decreased caloric intake and increased diet duration, not with reduced carbohydrate content”.5 However, as Dr. Joel Kauffman recently pointed out,6 that is a misleading conclusion. In the true low-carbohydrate group, the mean weight loss in trials was 17 kilograms (37.4 pounds), while in the higher-carbohydrate group it was only two kilograms (4.4 pounds). Oddly, the authors do not consider this significant. Only by intermingling trials of low to medium and high-carbohydrate diets could the authors reach the misleading conclusion quoted above.6
Two New Atkins Diet Studies
Two new studies published in the respected Annals of Internal Medicine seem to provide further evidence that the Atkins diet is at least as effective as a low-fat/high-carb diet in helping people shred excess lard without harming their cholesterol levels. Dr. William Yancy and coworkers examined bodyweight, body composition, blood lipid levels and adverse effects over 24 weeks in 120 overweight, hyperlipidemic persons who were randomly assigned to follow the Atkins diet or a low-fat, low-cholesterol, reduced-calorie diet.7 The Atkins diet led to greater weight loss, reduction in blood triglyceride levels (harmful blood fats that may trigger heart disease) and increase in the HDL cholesterol (“good” cholesterol) level compared with the low-fat diet.
Further, investigators found that the LDL cholesterol (“bad” cholesterol) level did not change on average, but did increase by more than 10 percent from baseline to week 24 in 30 percent of recipients of the Atkins diet who completed the study. In fact, two participants in the Atkins group dropped out of the study because of concerns about elevated blood lipid levels. Also, several symptomatic adverse effects occurred more frequently in the Atkins diet group, including constipation, headache, diarrhea, general weakness, etc. The authors concluded that over 24 weeks, healthy hyperlipidemic persons who followed the Atkins diet lost more bodyweight and body fat than did those who followed a low-fat diet. As the authors pointed out, the monitoring of blood lipid levels remains important because a small percentage of persons may experience adverse effects.
However, investigators could not definitively distinguish the effects of the Atkins diet and those of the nutritional supplements (multivitamin/mineral formula, essential oil formula, diet formula) provided only to that group. For example, the diet formula contained 3,000 milligrams of carnitine and this substance might be an effective supplement in low-carb/high-fat diets. Certainly, oral carnitine supplementation results in increased blood and tissue levels of carnitine. The higher doses of carnitine may lead to increased systematic and hepatic carnitine and may also lead to increased free fatty acid utilization and increased fat tissue breakdown.10
The second Atkins diet study published in the same issue of the journal found similar weight loss in persons randomly assigned to the Atkins diet or a conventional high-carb/low-fat diet for one year. However, the Atkins diet group
had a direct and more favorable effect on triglyceride level, “good” cholesterol level and glycemic control in the smaller subgroup of patients with diabetes.
Harvard Professor Credits Dr. Atkins, but Skeptics Remain
In an accompanying editorial, Dr. Walter Willett, from the Harvard School of Public Health, wrote: “We can no longer dismiss very-low-carbohydrate diets… Dr. Atkins deserves credit for his observations that many persons can control their weight by greatly reducing carbohydrate intake and for his funding of trials by independent investigators.”9
However, critics say there is still serious doubt about the long-term effect on health of adopting the Atkins diet. For example, Dr. David Katz, clinical professor of public health and medicine at Yale University, said: “I do not feel this topic should be studied at all.” What the f--k?! We should not study low-carb diets at all? That´s ridiculous nonsense!
“The public has been misled enough already,” said Dr. Robert Eckel, a nutrition spokesman for the American Heart Association (AHA) and a professor of medicine and physiology at the University of Colorado Health Science Center. Hmm… misled enough already? Eckel, dude, do you remember the 2001 protein statement by the AHA Nutrition Committee that turned out to be nothing but a bunch of horseshit?
