Wednesday, October 14, 2015

Non-Adherence and Design Problems: Two Reasons Why Recent Diet Study May Fail to Show Benefits of High(er) Protein + Dairy Intakes in Overfat (>37%) Women

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.
What's better a calorie reduced diet with the suggested amount of protein or one with a slightly higher amount of protein and extra low-fat dairy in it, when it comes to shedding the exuberant body fat off the hips, abs and buttocks of 104 overweight / obese (or with a body fat content of 37%+ "overfat") premenopausal women?

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.
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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)
If you look at the tabular overview of what the subjects eat (I won't reprint 4 pages from the full text here) you can easily get confused and think that there were five different groups, eventually it does yet all come down to two groups, the intervention (INT) and comparison (COM) groups and their different diets during the previously explained phases of the study.
Figure 1: Macronutrient compositions of the prescribed diets in the intervention and comparison group (Shlisky. 2015).
In that, the most significant inter-group difference were (a) the macronutrient composition with 30% PRO, 25% FAT, 45% CHO in the intervention group (INT) and 16-17% PRO, 24-25% FAT, 59% CHO in the comparison group (COM).
Figure 2: Total intake (g) of carbohydrates, proteins and fats during the 12 week weight loss and maintenance phases (Shlisky. 2015)
"[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) 
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).
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!
What does previous research tell us? If you look at previous research by Bowen (2004 & 2005), Josse (2011), Thorpe (2008) and Zemel (2004), there is significant evidence that high(er) protein intakes will augment fat loss and lean mass retention while increased dairy intakes may benefit bone mass and metabolic markers in men, women, young and old. In particular, when they are consumed alongside true exercise regimen, high(er) protein intakes have been proven have additive effects on body comp. during weight loss (8.8kg vs. 5.5kg fat loss in 16wks | Layman. 2005).

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).
Needless to say that the novelty of the physical activity, of which I'd like to remind you that it had the same volume for both groups, must be taken into consideration when we take a look at the results of the 24-wk study:
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).
Now, if you look at the overall effects and inter-group differences in Figure 3, three things are remarkable: Firstly, all subjects lost a significant amount of body weight and body fat without having to starve themselves or spending hours on the elliptical or treadmill. Secondly, there were no inter-group differences, which means that neither the overall increase in protein intake (see Figure 2), nor the increased intake of low-fat dairy and most prominently yogurt (effectively, the difference was only 1 serving per day, because the INT subjects failed to hit their target of five and ate only four servings per day) had beneficial effect on (a) the actual weight and more importantly fat / lean mass loss and (b) the subjects' general ability to keep the weight off during the follow up.
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)
If we also take into account the data from Figure 3 which depicts the reduction in energy intake from baseline and the total number of steps participants in both groups took on a daily basis, we could yet conclude that the lower dairy (no yogurt) + lower protein group achieved very similar results with less efforts. There is thus no debating the scientists conclusion that
"[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.
The actual macronutrient ratio during the weight loss and maintenance phase (figure shows averages) was by no means what it was supposed to be. The women ate ~8% less protein than they were supposed to do.
So, there's no benefit to high(er) protein and dairy intakes? No, there isn't - at least in a study with such a questionable design. Did you recognize the culprit? Yes, you're right: What on earth do you expect to happen if you design a "weight maintenance phase" during which the subjects still have to consume an energy reduced diet... I mean, it is well possible that the dietitians equations said that the diet was "energy-balanced". If you compare their intake to the ad-libitum diets of the subjects (=their baseline diet), the women still consumed 18% (HP) and 27% (NP) less energy during the weight maintenance phase - this time with a significant inter-group difference in favor of the high(er) protein high(er) dairy (yogurt) group who consumed more energy during both the weight loss and maintenance phase with identical results.

I am not sure what you think, but I personally would refute any statement about the standard diet recommendation being as efficient as a high(er) protein + high(er) dairy variety based on the study at hand. The increased satiety effect, a potential increase in thermogenesis, etc. - all the purported benefits of high(er) protein intakes couldn't show due to (a) non-adherence (instead of 30%, the subjects in the intervention group consumed only 23% and 20% protein during the weight loss and maintenance phase, respectively, and were thus not far off of the 20% and 18% in the COM group) and (b) the stupid idea not to let the women eat an ad-libitum with a fixed macronutrient ratio during the weight maintenance phase. This is after all a more realistic scenario and one in which real benefits of high(er) protein can show | Comment on Facebook!
References:
  • 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.