|This could not be a meal from the study too few carbohydrates... even for the medium CHO group.|
What may be surprising, though, is that the statistics based conclusion of a recent study that determined the effects of 16-week high[er]-dairy-protein, variable-carbohydrate diets and exercise training on body composition in men and women with overweight/obesity says: "Compared to a healthy control diet, energy-restricted high-protein diets containing different proportions of fat and CHO confer no advantage to weight loss or change in body composition in the presence of an appropriate exercise stimulus" (Parr. 2016).
If this is not your first visit to www.suppversity.com, you will probably be here, because you know that I never settle for a 1-2 sentence conclusion from an abstract - and guess what: If you take a look at the actual study outcomes, it turns out that there is a noteworthy difference between the three diet groups, in which the participants, one hundred and eleven participants (age 47 6 6 years, body mass 90.9 +/- 11.7 kg, BMI 33 +/- 4 kg/m², values mean +/- SD) were randomly stratified to one of the following (isocaloric) three diets:
- High dairy protein, high CHO (HDPHC; 30% protein, 55% CHO, 15% fat; 41 dairy servings/day of sweetened, low-fat products)
- High dairy protein, moderate CHO (HDPMC; 30% protein, 40% CHO, 30% fat; 41 dairy servings/day of unsweetened/artificially sweetened, full-fat products)
- Low dairy protein, high CHO (CON; 15% protein, 55% CHO, 30% fat: 1-2 dairy servings/day)
requirements (Frankenfield. 2005).
"[...p]articipants met fortnightly with a dietitian and were provided with edu cation resources. Menus for each diet provided for three meals/day and a “Dairy/Snack Basket” (food choices that achieved most of the nutrient manipulation for each diet; Table 1). For the higher protein diets, the Baskets contained foods equivalent to four to five dairy servings (NHMRC. 2011) where two servings were to be consumed as soon as practical post-EXT. In the moderate-protein CON diet, “Baskets” provided CHO-rich choices (e.g., non-dairy) for post-EXT recovery snacks and meal additions" (Parr. 2016).To optimize fat and minimize muscle loss, all participants had to follow the same combined resistance (REX) plus aerobic exercise (EXT) training:
- REX - 3 sessions per week (total 48 sessions in 16 weeks) of an individualized training program; a range of exercises were employed to train the same muscle groups (chest, back, legs and core) for 3-4 sets of 8-15 reps at 40-70% of 1RM. Exercise diaries kept by the study trainers were used to ensure the appropriate weight and number of sets was completed.
- EXT - 4 sessions on days without REX equating to 250 kcal/day energy expenditure; more specifically, the subjects performed exercises such as a 4 km walk, 16 km cycle or 1 km swimming, or equivalent combinations
|Figure 1: Effects of a 16-week diet and exercise intervention on the percentage change relative to baseline in (left) fat mass, and (right) lean mass (LM) for three different diets (Parr. 2016).|
In that, the lean mass advantage of the high protein medium carbohydrate group (HDPMPC) is most meaningful in the first 8 weeks - meaningful enough to be practically relevant, albeit not statistically significant over the complete 16 week study period. Even if ...
- the body mass loss in the three groups was virtually identical (HDPMC: 27.2 +/- 3.3 kg; HDPHC: 27.0 +/- 3.3 kg; CON: 27.7 +/- 3.6 kg; P = 0.42), and
- the loss of body fat in all groups was significant in both absolute and relative-to-baseline changes across, but not significantly different
The lean mass retention or rather increase in the high protein groups may later literally turn the scale, when the high protein, medium carbohydrate group (HDPMPC) don't experience the same weight rebound as the subjects in the CON and maybe even the HDPHPC group, where the resting energy expenditure started to plummet more steeply after 8 weeks of dieting (see Figure 2).
This is no "high protein diet" study as the ones by Jose Antonio the total protein intake in the so-called "high protein" groups averaged ~110-120g and was thus hardly more than 1.3g/kg body weight. In view of the fact that the only really tightly controlled study on the effects of protein intake on weight and fat loss shows optimal results with a similar protein intake (1.6g/kg) at albeit overall much lower total energy intakes, it is also questionable, whether the lack of significant differences in the study at hand has anything to do with the "low" protein intakes in the high protein groups.Additional non-significant benefits of the HDPMPC diet compared to the CON diet that were reported only as supplementary data, yet not in the full-text, were:
Figure 2: Effects of the diet intervention on total energy expenditure er day (Parr. 2016).
- greater reductions in trunk fat and greater increases in trunk lean mass,
- greater reductions in leg fat and greater increases in leg lean mass, as well as
- greater reductions in glucose, insulin, HOMA-IR, and total cholesterol.
Yes, none of these changes was statistically significant, and still... they occurred over only 16 weeks and the way the energy expenditure (Figure 2) develops, the advantage of the HDPMPC (open squares) over the MDPHDC (black triangles) and the HDPMDC (black circles) diet is going to increase, not decrease over time.
- Frankenfield, David, et al. "Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review." Journal of the American Dietetic Association 105.5 (2005): 775-789.
- National Health and Medical Research Council (NHMRC). A modelling system to inform the revision of the Australian Guide to Healthy Eating. In: Australian Dietary Guidelines, Dietitans Association of Australia, K. Baghurst, L Cobiac, P Baghurts and A. Magarey, eds. Chapter 3, Table 4. Canberra: Commonwealth of Australia; 2011, pp 1-621.
- Parr, Evelyn B., et al. "A randomized trial of high‐dairy‐protein, variable‐carbohydrate diets and exercise on body composition in adults with obesity." Obesity (2016).