"I literally called up my editor and said, 'I just got off the phone with so-and-so, and he's [taken] credit for getting Americans to eat less eggs and less fat. This guy's one of the worst scientists I've ever talked to, and if he was involved in this, then there's a story there."
For decades, well-meaning health authorities have proudly taught us that a diet low in fat and high in starch promotes fat loss. However, there's little, if any, scientific evidence supporting this notion.
Meta-analyses of studies (a quantitative method of combining the results of independent studies) that mostly lasted six months or less suggest a small benefit for low-fat diets compared with moderate-fat diets.
However, patients on low-fat diets typically regain lost weight. Furthermore, two meta-analyses of studies lasting one year or more found no sustained reduction in weight, even though the low-fat group had more intense interventions, which would create bias in their favor.
Gym rats already know what science is now showing. Replacing carbs (especially processed carbs) with protein and fat is an effective way to promote fat burning while sparing muscle mass, so it would be wise not to follow the dietary guidelines of the American Heart Association or the American Dietetic Association.
The old notion of "a calorie is a calorie" is clearly an incorrect approach to body composition alterations. I'm not going to review all the related studies. Rather, I will ask you to just look at Figures 1 and 2.
Figure 1. Layman et al. showed that a high-protein/moderate-carb diet is superior to a high-carbohydrate diet with respect to overall body composition. Adapted from Antonio J. Manninen, AH. Eating to improve body composition. In: Antonio J. et al. eds. Essentials of Sports Nutrition and Exercise (in press).
Figure 2. Feinman computed the energy lost by comparing fat to lean body loss from McAuley's data.* The low-carbohydrate diet (Atkins) has an advantage over the other diets, even though this group consumed more calories. Triangles, Atkins diet; squares, Zone diet; circles, high-carb/low-fat diet. (*McAuley KA et al. Comparison of high-fat and high-protein diets with a high-carbohydrate diet in insulin-resistant obese women. Diabetologia, 2005;48:8-16).
Another enduring urban legend is that protein requirements for bodybuilders and other strength-power athletes are only slightly higher than the current recommended dietary allowance (RDA) of 0.8 grams of protein per kilogram of bodyweight. It should be noted, however, that serious gym rats are not concerned with minimum protein requirements.
|RDA RECOMMENDATION PROTEIN CALCULATOR|
Rather, they want to maximize muscular gains. Dr. Fern and colleagues compared protein intakes in bodybuilders assigned to either 3.3 or 1.3 grams per kilogram per day. The results indicated that protein synthesis (i.e., anabolism) increased with training regardless of diet. However, the increase in synthesis was fivefold greater with the higher protein intake.
Amino acid burning also increased on the higher intake, suggesting optimal protein intake was also exceeded. Although more research is needed, it appears that gym rats should take in about 2.0 to 2.5 grams of protein per kilogram of bodyweight. With that said, this article examines the latest scientific findings related to bodybuilding nutrition.
|GYM RAT PROTEIN CALCULATOR|
Decreases Caloric Intake
Numerous studies have reported that high-protein/low-carb diets reduce appetite and thus, caloric intake. Recently, Dr. David Weigle and co-workers at the Oregon Health and Science University tested the hypothesis that increasing the protein content while maintaining the carb content of the diet lowers bodyweight by decreasing appetite and spontaneous caloric intake.
Appetite, Caloric Intake, Bodyweight & Fat Mass Were Measured In 19 Subjects Placed Sequentially On The Following Diets:
- A weight-maintaining diet (15% protein, 35% fat, 50% carb) for two weeks
- An isocaloric diet (30% protein, 20% fat, 50% carb) for two weeks
- An ad libitum (self-directed) diet (30% protein, 20% fat, 50% carb) for 12 weeks.
Not surprisingly, the subjects reported a clear decrease in hunger and an increase in fullness during weeks three and four of the study after the transition to the high-protein diet. This increase in satiety was confirmed by a significant decrease in spontaneous caloric intake.
The authors concluded,
The authors also suggested that less emphasis should be placed on carb restriction without regard for concomitant increases in dietary fat.
In conclusion, if you want to shred extra lard, the high-protein diet is the way to go.
High protein intake has no adverse effects on bones, liver or healthy kidneys. Also, a recent study published in the Annals of Internal Medicine suggests that increased intake of protein may play an important role in preventing and treating high blood pressure.
High-Protein/Low-Carb Diets & Skeletal Muscle Protein Synthesis
Compared with high-carb/low-fat diets, short-term very-low-carb diets consistently result in improvements in fat loss, blood lipids and insulin resistance. However, some old school nutritionists have incorrectly suggested that very-low-carbohydrate intake leads to progressive loss of muscle mass.
According to Dr. Barbara Moore of Shape Up America!,
When that [glucose] runs out, you start to feel a little light-headed, fatigued, confused and maybe even a little nauseated because your brain is now more desperate for glucose. It starts breaking down body protein. Muscle protein, including heart protein, becomes a target for your body to convert to glucose."
What a load of bulls@$t! Even apes are intelligent enough to realize that the last thing the body wants to break down is the heart. True, animals share the metabolic deficiency of the total (or almost total) inability to convert fatty acids to glucose (blood sugar).
So, the primary source for a substrate for gluconeogenesis (the formation of glucose from non-carbohydrate molecules) is amino acid, a building block of protein, with some help from glycerol from fat tissue triglycerides (i.e., storage form of fat; contains one glyceride molecule plus three fatty acid molecules).
However, when the rate of mobilization of fatty acids from fat tissue is accelerated, as, for example, during a very-low-carb diet, the liver produces ketone bodies.
The liver cannot utilize ketone bodies and thus, they flow from the liver to extra-hepatic (outside the liver) tissues (e.g., brain, muscle) for use as a fuel.
Simply stated, ketone body metabolism by the brain displaces glucose utilization and thus spares muscle mass. In other words, the brain derives energy from storage fat during a very-low-carb diet.
University Of Michigan Study
A recent well-controlled study Dr. Matthew Harber and co-workers at the University of Michigan examined the influence of a very-low-carb/high-protein diet on skeletal muscle protein synthesis and whole-body protein degradation. Eight healthy subjects volunteered for participation in this study.
After being admitted to the hospital, the subjects ate a standardized diet for two days consisting of 60 percent of total energy from carbs, 30 percent from fat and 10 percent from protein. During the one-week, very-low-carb/high-protein diet, the subjects consumed a weight-maintaining diet consisting of five percent of total energy from carbs, 60 percent from fat and 35 percent from protein.
The main finding of this study was that the skeletal muscle protein synthesis increased despite strict carb restriction and a dramatic reduction in insulin levels. The increase in skeletal muscle anabolism was accompanied by an increase in whole-body protein degradation.
The Bottom Line
So, what is the bottom line? Well, this study confirmed that a very-low-carb/high-protein diet certainly does not lead to progressive loss of muscle mass.
However, this study also suggests that a very-low-carb diet is not ideal if your primary goal is to increase muscle mass, as the increase in muscle anabolism was accompanied by an increase in whole-body protein breakdown.
Furthermore, low carb intake can decrease exercise performance. There is strong evidence that resistance training, especially using free-weight exercises with high training volumes and moderate loads, is partially dependent upon glycogen (carb) stores.
Thus, carb ingestion prior to, during and after resistance exercise may improve performance and speed recovery, which could ultimately magnify the muscle-building response to exercise.
Proteins & Cardiovascular Health
A recent literature review by Dr. Frank Hu at the Harvard School of Public Health published in the American Journal of Clinical Nutrition provided an overview of experimental and epidemiologic evidence regarding the role of protein in cardiovascular health. The key take-home messages were as follows:
- Exchanging animal protein for carbohydrates in human diets significantly reduces bad cholesterol (LDL) and triacylglycerol levels and increases good cholesterol (HDL) levels.
- Higher consumption of protein has been inversely associated with blood pressure in several observational studies and animal experiments. In other words, higher protein intake decreases blood pressure.
- Some studies suggest a positive association of heart disease mortality rates with animal protein consumption and an inverse association with vegetable protein consumption.
As pointed out by Dr. Hu, however, this result should be interpreted with caution because the countries with a higher protein intake also have higher intakes of saturated fat and cholesterol and lower intake of fiber.
- Interestingly, a significant decline in the incidence of stroke in Japan in the past decades has been attributed to increased consumption of animal products, including meat, eggs and dairy (as well as improved pharmacologic treatment of hypertension).
- The use of a plant source of protein may provide even greater health benefits and should therefore be considered simultaneously.
Dubious Registry On Successful Losers
Another paper published in the American Journal of Clinical Nutrition presented some of the major findings from the National Weight Control Registry (NWCR), a database of some 4,000 individuals who have purportedly been successful at long-term weight loss maintenance.
The Authors Suggested Six Key Strategies For Long-Term Success At Weight Loss:
- Engaging in high levels of physical activity.
- Eating a diet low in calories and fat.
- Eating breakfast.
- Self-monitoring weight on a regular basis.
- Maintaining a consistent eating pattern.
- Catching "slips" before they turn into larger regains.
It should be noted, however, that the NCWR is a completely uncontrolled registry, so I feel it has no scientific value. Contrary to popular belief supported by the well-meaning NWCR people, well-controlled studies suggest that high-fat diets do not appear to be the primary cause of obesity, and reductions in fat will not be a solution.
Also, there are several studies showing a decrease in testosterone levels in individuals consuming a diet containing about 20 percent fat compared with a diet containing about 40 percent fat.
- Willett WC. Reduced-carbohydrate diets: no roll in weight management? Ann Intern Med, 2004;140:836-837.
- Manninen AH. Is a calorie a calorie? Metabolic advantage of low-carbohydrate diets. J Int Soc Sports Nutr, 2004;1(2):21-26.
- Layman DK. A reduced ratio of dietary carbohydrate to protein improves body composition and blood lipid profiles during weight loss in adult women. J Nutr, 2003;133:411-417.
- Fern EB et al. Effects of exaggerated amino acid and protein supply in man. Experientia, 1991;15:168-72.
- Weigle DS et al. A high-protein diet induces sustained reductions in appetite, ad libitum caloric intake, and body weight despite compensatory changes in diurnal plasma leptin and ghrelin concentrations. Am J Clin Nutr, 2005;82:41-48.
- Manninen AH. High-protein weight loss diets and purported adverse effects: where is the evidence? Sports Nutr Rev J, 2004;1(1):45-51.
- Manninen AH. High-protein diets are not hazardous for the healthy kidneys. Nephrol Dial Transplant, 2005;20:657-658.
- He J et al. Effect of soybean protein on blood pressure: a randomized, controlled trial. Ann Intern Med, 2005;143:1-9.
- Volek JS, Sharman MJ. Cardiovascular and hormonal aspects of very-low-carbohydrate ketogenic diets. Obes Res, 2004;12:115S-23S.
- Manninen AH. Metabolic effects of very-low-carbohydrate diets: misunderstood "villains" of human metabolism. J Int Soc Sports Nutr, 2004;1(2):7-11.
- Harber MP et al. Effects of dietary carbohydrate restriction with high protein intake on protein metabolism and the somatotropic axis. J Clin Endocrinol Metab, 2005 Jun 21 (Epub ahead of print).
- Haff GG et al. Carbohydrate supplementation and resistance training. J Strength Cond Res, 2003;17:187-96.
- Hu F. Protein, body weight, and cardiovascular health. Am J Clin Nutr, 82:242S-247S.
- Wing RR, Phelan S. Long-term weight loss maintenance. Am J Clin Nutr, 2005;82:222S-225S.
- Willett WC, Leibel RL. Dietary fat is not a major determinant of body fat. Am J Med, 2002 Dec 30;113 Suppl 9B:47S-59S.