Malingering’s World

Thanks to CrossFit and myself not wanting to be one of the sheep following blindly without thinking for myself, I’ve become caught up in the low carb vs. “a calorie is a calorie” debate. It seems the low carb people are
making more money right now (though weight watchers does pretty well), but what does that mean exactly? There is no doubt that low carb diets do work for people, however I’m having trouble finding evidence that shows they work via their purported mechanisms. For most people, they work via calorie restriction, which is not fancy at all and really indicates that everyone should just try to get along and eat less, regardless of how they do it.

(Note: I’m also rather interested in this whole “low carb works and no one wants to admit it” crap that I’ve been hearing from way way too many people. Um, people have admitted it. Why do you think there are South Beach bars in the store and Zone frozen entrees in the freezer section, and every low carb book that comes out these days is on the bestseller list? People have admitted it, time and time again, and I’m still reading over and over that people haven’t accepted it.)

So today, we will look at 3 articles that say macronutrient composition (namely, carb restriction) is important for weight loss, and 3 articles that say it doesn’t make any difference. I am attaching abstracts for all 6 articles. Note that I am focusing here on weight loss. Nothing else.

****Low carb diets are the answer****

Twenty men were put on either low carb or low fat diets for 4 weeks. They could pretty eat as much as they wanted to within the guidelines. Low carb people averaged about 22g carbs/day and 1732 calories/day. Low fat people averaged about 170g carbs/day and about 1900 calories/day. Weight loss: low carb averaged a loss of 13.9lbs, low fat averaged a loss of 8.8lbs. While the calories weren’t kept consistent, it appears the amount of difference in weight loss cannot be entirely accounted for by calories differences if you use the general rule that 3500 calories = 1 pound, the difference would only be a pound and a half, not 5lbs. American Journal of Clinical Nutrition, Vol. 87, No. 1, 44-55, January 2008

Background: Altering the macronutrient composition of the diet influences hunger and satiety. Studies have compared high- and low-protein diets, but there are few data on carbohydrate content and ketosis on motivation to eat and ad libitum intake. Objective: We aimed to compare the hunger, appetite, and weight-loss responses to a high-protein, low-carbohydrate [(LC) ketogenic] and those to a high-protein, medium-carbohydrate [(MC) nonketogenic] diet in obese men feeding ad libitum. Design: Seventeen obese men were studied in a residential trial; food was provided daily. Subjects were offered 2 high-protein (30% of energy) ad libitum diets, each for a 4-wk period—an LC (4% carbohydrate) ketogenic diet and an MC (35% carbohydrate) diet—randomized in a crossover design. Results: Ad libitum energy intakes were lower with the LC diet than with the MC diet [P = 0.02; SE of the difference (SED): 0.27] at 7.25 and 7.95 MJ/d, respectively. Over the 4-wk period, hunger was significantly lower (P = 0.014; SED: 1.76) and weight loss was significantly greater (P = 0.006; SED: 0.62) with the LC diet (6.34 kg) than with the MC diet (4.35 kg). The LC diet induced ketosis with mean 3-hydroxybutyrate concentrations of 1.52 mmol/L in plasma (P = 0.036 from baseline; SED: 0.62) and 2.99 mmol/L in urine (P < 0.001 from baseline; SED: 0.36). Conclusion: In the short term, high-protein, low-carbohydrate ketogenic diets reduce hunger and lower food intake significantly more than do high-protein, medium-carbohydrate nonketogenic diets.

Forty-eight women were studied over 4 months and were put into one of four groups, either high protein/low carb (about 100g protein and 130g carbs per day) or lower protein/higher carb (about 57g protein and 200g carbs/day). They were also divided into exercising or non-exercising groups. Average caloric intake was between 1900 and 2100 calories per day and was pretty even between the groups. High protein/low carb group lost about 20lbs, and the higher carb/lower protein group lost about 16lbs. A significant difference, though not huge. The exercising groups didn’t lose significantly more weight than the non-exercising groups, but their body fat percentages decreased significantly. J. Nutr. 135:1903-1910, August 2005

This study examined the interaction of 2 diets (high protein, reduced carbohydrates vs. low protein, high carbohydrates) with exercise on body composition and blood lipids in women (n = 48, ~46 y old, BMI = 33 kg/m2) during weight loss. The study was a 4-mo weight loss trial using a 2 x 2 block design (Diet x Exercise). Diets were equal in total energy (7.1 MJ/d) and lipids (~30% energy intake) but differed in protein content and the ratio of carbohydrate:protein at 1.6 g/(kg · d) and <1.5 (PRO group) vs. 0.8 g/(kg · d) and >3.5 (CHO group), respectively. Exercise comparisons were lifestyle activity (control) vs. a supervised exercise program (EX: 5 d/wk walking and 2 d/wk resistance training). Subjects in the PRO and PRO + EX groups lost more total weight and fat mass and tended to lose less lean mass (P = 0.10) than the CHO and CHO + EX groups. Exercise increased loss of body fat and preserved lean mass. The combined effects of diet and exercise were additive for improving body composition. Serum lipid profiles improved in all groups, but changes varied among diet treatments. Subjects in the CHO groups had larger reductions in total cholesterol and LDL cholesterol, whereas subjects in the PRO groups had greater reductions in triacylglycerol and maintained higher concentrations of HDL cholesterol. This study demonstrated that a diet with higher protein and reduced carbohydrates combined with exercise additively improved body composition during weight loss, whereas the effects on blood lipids differed between diet treatments.

26 people (half diabetic, half not) were studied over 3 months, eating either a low carb diet (average 56g carbs/day) or a healthy eating UK diet (average 163g carbs/day). This was NOT controlled for calorie intake, and the low carb people averaged about 1300 calories per day, whereas the other group averaged about 1600 calories per day. The low carb people lost more weight. They also ate less. Diabet Med. 2007 Dec;24(12):1430-5. 2007 Oct 29.

BACKGROUND: Low-carbohydrate diets are effective for weight reduction in people without diabetes, but there is limited evidence for people with Type 2 diabetes. Aims To assess the impact of a low-carbohydrate diet on body weight, glycated haemoglobin (HbA(1c)), ketone and lipid levels in diabetic and non-diabetic subjects. METHODS: Thirteen Type 2 diabetic subjects (on diet or metformin) and 13 non-diabetic subjects were randomly allocated to either a low-carbohydrate diet (< or = 40 g carbohydrate/day) or a healthy-eating diet following Diabetes UK nutritional recommendations and were seen monthly for 3 months. Subjects (25% male) were (mean +/- sd) age 52 +/- 9 years, weight 96.3 +/- 16.6 kg, body mass index 35.1 kg/m(2), HbA(1c) 6.6 +/- 1.1%, total cholesterol 5.1 +/- 1.1 mmol/l, high-density lipoprotein cholesterol 1.3 +/- 0.4 mmol/l, low-density lipoprotein cholesterol 3.1 +/- 0.9 mmol/l, triglycerides (geometric mean) 1.55 (1.10, 2.35) mmol/l and ketones range 0.0-0.2 mmol/l. RESULTS:Analysis was by intention to treat with last observation carried forward. Twenty-two of the participants (85%) completed the study. Weight loss was greater (6.9 vs. 2.1 kg, P = 0.003) in the low-carbohydrate group, with no difference in changes in HbA(1c), ketone or lipid levels.

****A calorie is a calorie is a calorie****

This study watched people for 12 weeks and very carefully controlled the amount of fat, protein, and carbs. Everyone lost weight. Hooray! And the composition turned out to be insignificant. Am J Clin Nutr. 2004 May;79(5):899S-906S.

The aim of this review was to evaluate data regarding potential thermodynamic mechanisms for increased rates of weight loss in subjects consuming diets high in protein and/or low in carbohydrate. Studies that compared weight loss and energy expenditure in adults consuming diets high in protein and/or low in carbohydrate with those in adults consuming diets low in fat were reviewed. In addition, studies that measured the metabolizable energy of proteins, fats, and carbohydrates were reviewed. Diets high in protein and/or low in carbohydrate produced an approximately equal to 2.5-kg greater weight loss after 12 wk of treatment. Neither macronutrient-specific differences in the availability of dietary energy nor changes in energy expenditure could explain these differences in weight loss. Thermodynamics dictate that a calorie is a calorie regardless of the macronutrient composition of the diet. Further research on differences in the composition of weight loss and on the influence of satiety on compliance with energy-restricted diets is needed to explain the observed increase in weight loss with diets high in protein and/or low in carbohydrate.

This study I’ve mentioned before. In 1992, they locked up 16 people and gave them liquid diets with varying levels of fat or carbs. Low carb/high fat proponents would hope that people on the 70% fat/30% carbs diet would lose more weight than the people on 100% carbs/0% fat diet, but in the end, it was all the same. Am J Clin Nutr. 1992 Feb;55(2):350-5.

Diets rich in fat may promote obesity by leading to a greater deposition of adipose-tissue triglycerides than do isoenergetic diets with less fat. This possibility was examined by a retrospective analysis of the energy needs of 16 human subjects (13 adults, 3 children) fed liquid diets of precisely known composition with widely varied fat content, for 15-56 d (33 +/- 2 d, mean +/- SE). Subjects lived in a metabolic ward and received fluid formulas with different fat and carbohydrate content, physical activity was kept constant, and precise data were available on energy intake and daily body weight. Isoenergetic formulas contained various percentages of carbohydrate as cerelose (low, 15%; intermediate, 40% or 45%; high, 75%, 80%, or 85%), a constant 15% of energy as protein (as milk protein), and the balance of energy as fat (as corn oil). Even with extreme changes in the fat-carbohydrate ratio (fat energy varied from 0% to 70% of total intake), there was no detectable evidence of significant variation in energy need as a function of percentage fat intake.

Here we have 43 people locked up for 6 weeks. They either had a diet made up of 15% carbs or 45% carbs and they went about their business. In the end, in fact, there was no difference in the amount of weight they lost. Oh well.
American Journal of Clinical Nutrition, Vol 63, 174-178, Copyright © 1996

The goal of this study was to evaluate the effect of diets that were equally low in energy but widely different in relative amounts of fat and carbohydrate on body weight during a 6-wk period of hospitalization. Consequently, 43 adult, obese persons were randomly assigned to receive diets containing 4.2 MJ/d (1000 kcal/d) composed of either 32% protein, 15% carbohydrate, and 53% fat, or 29% protein, 45% carbohydrate, and 26% fat. There was no significant difference in the amount of weight loss in response to diets containing either 15% (8.9 +/- 0.6 kg) or 45% (7.5 +/- 0.5 kg) carbohydrate. The results of this study showed that it was energy intake, not nutrient composition, that determined weight loss in response to low-energy diets over a short time period.