|Don't expect weight loss wonders from high(er) protein and dairy intakes, but especially when the energy intake is not controlled both can have benefits the study at hand could not detect.|
That's probably not exactly the way the scientists from the Utah State University, the Pennsylvania State University, the University of Illinois and the FB Technical Center (Shlisky. 2015) would phrase their research question, but in the end, their 24-week three-phase randomized weight loss intervention comes tried to answer exactly this question.
To learn more about the impact of higher protein intakes (30% vs. 20% of total energy intakes) and the purported "magic" of diets that are high in low fat dairy (in particular yogurt), Julie D. Shlisky and her colleagues had their subjects go through a three-phase weight loss intervention with
- the JumpStart phase (weeks 0–2), being intended to kickstart the subjects' weight loss on a ~35% energy deficit, phase (2),
- the Weightloss phase (weeks 3–12; total of 12 weeks), during which the subjects were supposed to adhere to a 1,500-1,700kcal diet which came close to a 25-30% energy deficit compared to their baseline energy intakes, and
- the Weightloss Maintenance phase, (weeks 13–24; total of 12 weeks), over the course of which the subjects had to stick to a dietitian designed "energy-balanced" diet which had still ~20% less energy than the subjects baseline diet (see Figure 4, right)
|Figure 1: Macronutrient compositions of the prescribed diets in the intervention and comparison group (Shlisky. 2015).|
In addition, the subjects were told to consume 5 servings per day (with a focus on low fat yogurt) in the intervention and 3 servings of dairy (excluding yogurt) in the comparison group, as well as to finally get their behind off the couch for a total of ~8,000-10,000 steps per day (that was ~30-40 minutes of walking per day).
"[w]eekly educational sessions were held for both INT and COM groups throughout the 6- month study and included lessons on basic nutrition knowledge, exchange patterns of eating, portion size and control, purchasing and preparing food and modifying recipes as well as motivational lessons on outcome expectations, selfregulation and monitoring, problem- solving, lifestyle modification, emotion eating and motivation for walking" (Shlisky. 2015)
Figure 2: Total intake (g) of carbohydrates, proteins and fats during the 12 week weight loss and maintenance phases (Shlisky. 2015)
|Thorpe et al. were able to show that high(er) protein intakes from dairy will decrease calcium loss and preserve bone mass (WB = whole body; LS = lumbar spine) while dieting. Don't fall for the "protein is bad for your bones" lie!|
Against that background I would be very hesitant to take use the study at hand to argue that you can shed body fat just as effectively on the bogus "recommended diet" (=15-20% protein, 60% carbohydrates and 20-25% fat).
|Figure 3: Relative changes in markers of body composition after the weight loss and weight maintenance phase; all values expressed as percent difference to the respective pre-values in both groups (Shilsky. 2015).|
|Figure 4: Reduction in energy expenditure (% of baseline) and total step count (activity level) of the subjects in the weight loss and weight maintenance phases of the study (Shlisky. 2015)|
"[h]ealthy premenopausal women with excess adiposity effectively lost BW and fat mass and improved some metabolic risk factors following an ERD with approximately 20% protein and 3 svg/d of nonfat dairy intake." (Shlisky. 2015)The increased protein or dairy (in this case mostly yogurt) intake did after all not offer significant benefits, as neither of the existing differences in Figure 3 was statistically significant.
- Bowen, Jane, Manny Noakes, and Peter M. Clifton. "A high dairy protein, high-calcium diet minimizes bone turnover in overweight adults during weight loss." The Journal of nutrition 134.3 (2004): 568-573.
- Bowen, J., M. Noakes, and P. M. Clifton. "Effect of calcium and dairy foods in high protein, energy-restricted diets on weight loss and metabolic parameters in overweight adults." International journal of obesity 29.8 (2005): 957-965.
- In particularly in conjunction with exercise, high(er) protein intakes have been proven have additive beneficial effects on body composition during weight loss (Layman. 2005)
- Josse, Andrea R., et al. "Increased consumption of dairy foods and protein during diet-and exercise-induced weight loss promotes fat mass loss and lean mass gain in overweight and obese premenopausal women." The Journal of nutrition 141.9 (2011): 1626-1634.
- Shlisky, Julie D., et al. "An energy‐reduced dietary pattern, including moderate protein and increased nonfat dairy intake combined with walking promotes beneficial body composition and metabolic changes in women with excess adiposity: a randomized comparative trial." Food Science & Nutrition (2015).
- Thorpe, Matthew P., et al. "A diet high in protein, dairy, and calcium attenuates bone loss over twelve months of weight loss and maintenance relative to a conventional high-carbohydrate diet in adults." The Journal of nutrition 138.6 (2008): 1096-1100.
- Zemel, Michael B., et al. "Calcium and dairy acceleration of weight and fat loss during energy restriction in obese adults." Obesity research 12.4 (2004): 582-590.