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Sabtu, 23 Januari 2016

Overeating = Natural Response to Strict Dieting That Occurs Despite Increased Satiety Hormone Response to XXL-Meal

This is not a photo from the full-text of the study, but it could be. After all the energy deficient diet was >90% below the maintenance intakes of the subjects. That's unfortunately much more severe than the average dieter's approach, but some of the things the scientists observed still have very general applications.
If you've ever dieted to make the cut in a sports with weight classes, you will know this insatiable hunger which climaxes on the last two days when you are down to a handful of  calories per day. It's a hunger that won't be satisfied even if you eat an extra 1000 kcal above maintenance.

Athletes competing in sports with weight classes may need to accept the post-dieting binge, but what about average Joes and Janes? Will a fasting day ruin the average dieters dieting efforts by making them eat more extra-calories on day 2 than they've economized the day before? A recent study from the US Army Research Institute of Environmental Medicine, in which scientists have attempted to stimulate and simulate this insatiable hunger in a tightly controlled experimental environment, may hold the answer.
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As Kristie L O'Connor et al. point out an altered secretion of appetite-mediating hormones is the #1 candidate to explain the common tendency for weight regain (Sumithran. 2013 | see Figure 1). This hypothesis is supported by several studies that have reported decreases in circulating leptin and insulin concentrations in response to weight loss that are disproportionately greater than contemporaneous reductions in fat mass (Mars. 2005; Blom. 2006; MacLean. 2006; Pasiakos. 2011; Sumithran. 2011). Other studies have documented blunted postprandial gastroenteropancreatic hormone responses after weight loss (Chan. 2004).

Figure 1: Selected pathways involved in body weight regulation (left) and tabular overview of physiological changes after diet-induced weight loss and their effect on energy intake and storage (right | Sumithran. 2013).
Scientists have speculated that these ill effects may be countered by eating diets with a low energy density and thus putting equivalent stress on the gastric mechanoreceptors in our guts. Unfortunately, this alone has turned out to be as ineffective as other attempts to minimize the adaptive response to energy restriction. On the other hand, the existing effects the volume of what we have will have on our satiety is something that has been overlooked in previous studies.
Figure 2: Study design. EB, energy balance; ED, energy deprivation; EE, energy expenditure; EI, energy intake; RMR, resting metabolic rate; TDEE, total daily energy expenditure; VAS, visual analogue scale (O'Connor. 2016).
Overall, our understanding of the complex relationship between what and how much we eat and how this affects our subjective satiety and corresponding hormone response is still very limited. To address this knowledge gap O'Conner et al. created 2 isovolumetric diets that differed in energy density but were otherwise comparable in taste, texture, and appearance that were fed to healthy young adults during a period of energy balance (EB) and a period of 90% energy deprivation (ED), in oder to "examine the physiologic effects of short-term ED on appetite-mediating hormones and appetite independent from reductions in diet volume" (O'Connor. 2016 | see Figure 2).
It is a common misunderstanding that you "must" lose your weight slowly: While most mainstream diet advise involves the recommendation that you shouldn't reduce your energy intake too significantly and that you must lose your weight slowly, the existing peer-reviewed experimental and observational evidence does not support the notion that (a) slow eight gain would support greater lean mass retention or (b) prevent weight regain. Learn why that's the case.
Figure 3: Overview of energy intake, deficits and macronutrient composition in the two study groups (O'Connor. 2016).
As the scientists had expected the energy deficit that was induced over two seperate 48-h periods during which the energy intake was matched to energy expenditure to maintain energy balance (EB) (-44 +/- 92 kcal/d) or yield less than 10% of the energy the subjects required (ED).

In conjunction with the low-to-medium intensity exercise regimen (0–65% VO2peak for 187 6 +/- 21 min/d) that burned an extra 1683 +/- 329 kcal/d, the ED group did thus end up having a whopping -3696 +/- 742-kcal/d deficit on each of the two days (!).

It is thus no wonder that the scientists observed a whole host of significant differences in the hormonal response to the "diet" (diet vs. fasting). One difference you probably know much better however, is depicted in Figure 4, which shows that the subjects in the ED group consumed not simply the amount of energy they needed on the subsequent ad-libitum meal condition, but an extra 811 kcal - and they still felt a significantly greater desire to eat right after and 180 minutes after the meal.
Figure 4: Energy intake on an ad-libitum (eat as much as you want) meal before and after the intervention (left)
and the corresponding desire to eat before and after the meal (right); the dotted line at 20 min in the right graph
indicates the time at which the ad-libitum meal was served (O'Connor. 2016).
Unfortunately, the complexity of the hormonal changes does not allow us to identify this one parameter we could target to counter this effect. With significantly reduced fasting insulin (256% 6 42%) and acyl ghrelin (260% 6 17%) concentrations, as well as leptin concentrations that decreased more during ED compared with EB (-47% 6 +/- 27% compared with -20% +/- 27%; P-interaction = 0.05), we have two three (expected) candidates that could explain the increased hunger and desire to eat before the ad-libitum meal. The increased postprandial insulin (57% +/- 63%; P < 0.001), GLP-1 (14% 6 28%; P = 0.04), and PP (54% +/- 52%; P < 0.001) areas under the curve (AUCs), as well as the reduced acyl ghrelin increase (-56% +/- 13%; P < 0.001) after ED compared with after EB, on the other hand, appear to contradict the lack of satiating effect of the 1834 kcal lunch in the 18–39 year-old healthy men and nonpregnant women who participated in the study at hand.
Intermittent Fasting Works, But is It Better Than "Regular" Dieting? What Do the Latest Reviews / Meta-Analyses Say? Find out in this SuppVersity Classic!
So what can be done? Well, the increase in appetite and desire to eat is probably a generally unavoidable effect of "starvation diets" and since this is what the study at hand focuses on, it is difficult to predict how pronounced the effect would have been if the ~3500kcal energy deficit, the subjects in the study at hand reached within just one day, would have been induced over the course of 3-5 days. A dieting approach like that would after all been much closer to what the average dieter does over the course of 3-5 days only to then overeat and fall off the wagon on the weekend. In addition, a lower calorie deficit may have (a) made it easier to identify what exactly it is that causes the rebound effect and may (b) have been insufficient to compensate for the binge.

This leads us directly to the most important result of the study at hand: As suboptimal as the diet may be, one significant and probably mostly underappreciated result of the study at hand is that - once again - the energy deficit you accumulate during a quasi-fast was not fully compensated for over the 36h follow up period. A fact that adds to the existing evidence in favor of cyclic diets as every-other-day fasting, where you cycle hunger and ad-libitum diet days | Comment!
References:
  • Blom, Wendy AM, et al. "Fasting Ghrelin Does Not Predict Food Intake after Short‐term Energy Restriction." Obesity 14.5 (2006): 838-846.
  • Chan, Jean L., et al. "Ghrelin levels are not regulated by recombinant leptin administration and/or three days of fasting in healthy subjects." The Journal of Clinical Endocrinology & Metabolism 89.1 (2004): 335-343.
  • Egecioglu, Emil, et al. "PRECLINICAL STUDY: FULL ARTICLE: Ghrelin increases intake of rewarding food in rodents." Addiction biology 15.3 (2010): 304-311.
  • MacLean, Paul S., et al. "Peripheral metabolic responses to prolonged weight reduction that promote rapid, efficient regain in obesity-prone rats." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 290.6 (2006): R1577-R1588.
  • Mars, Monica, et al. "Decreases in fasting leptin and insulin concentrations after acute energy restriction and subsequent compensation in food intake." The American journal of clinical nutrition 81.3 (2005): 570-577.
  • O'Connor, et al. "Altered Appetite-Mediating Hormone Concentrations Precede Compensatory Overeating After Severe, Short-Term Energy Deprivation in Healthy Adults." Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions (2016).
  • Pasiakos, Stefan M., et al. "Appetite and Endocrine Regulators of Energy Balance After 2 Days of Energy Restriction: Insulin, Leptin, Ghrelin, and DHEA‐S." Obesity 19.6 (2011): 1124-1130.
  • Sumithran, Priya, et al. "Long-term persistence of hormonal adaptations to weight loss." New England Journal of Medicine 365.17 (2011): 1597-1604.
  • Sumithran, Priya, and Joseph Proietto. "The defence of body weight: a physiological basis for weight regain after weight loss." Clinical Science 124.4 (2013): 231-241.

Kamis, 08 Oktober 2015

Resistance Training, Not Starving Yourself or "Cardio" is Key to Successful Fat (!) Loss -- Metabolic Stress Appears to Determine Improvements in Body Composition & Health

Just look at the guys surrounding you, girls. How on earth will you get bulky if they are training like maniacs and still look like size-zero bans?
"Overfat", that's a term scientists use to refer to obese, but more importantly over- or even normal-weight people who are still carrying exuberant amounts of body fat around. In a recent meta-analysis, James E. Clark from the Manchester Community College tried to figure out, which of the significant numbers of means of methods to alter body composition, and metabolic issues that are available for the adult who is overfat is the "best" one.

In his review, the scientists focused on comparing changes from treatment program for adults who are overfat based on analysis of aggregated effect size (ES) of inducing changes from 66-population based studies, and 162-studywise groups.
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Clark's analysis of this large dataset yielded both, obvious and less obvious results. The realization that "a hypocaloric balance [=dietary restriction] is necessary for changing body composition" (Clark. 2015), for example is hardly surprising.
Figure 1: There's little doubt that the overall improvements in body composition (figures are effect sizes for loss of fat, increase in lean mass) are the most pronounced in response to diet + resistance training (but non-existent w/ resistance training, only - not shown). What is surprising is the low efficacy of combined training programs, though (Clark. 2015).
What may be surprising, though is the fact that the available evidence indicates that the size and effectiveness of the caloric deficit "does not equate with the effectiveness for body compositional changes, or any biomarkers associated with metabolic issues" (Clark. 2015). In other words: It's not the guy or gal who diets the hardest who will lose the largest amounts of body fat.
Figure 2: The effect sizes of the interventions' effects on insulin, leptin, cholesterol & co yields similar results: The combination of resistance training and diet has (on average) the most favorable effects (Clark. 2015).
As the data in Figure 1 goes to show you, the combination with exercise is generally beneficial. In view of the fact that being "overfat" is also associated with being undermuscled, there's yet no reason to doubt Clark's conclusion that
"resistance training (RT) was more effective than endurance training (ET) or combination of RT and ET, particularly when progressive training volume of 2-to-3 sets for 6-to-10 reps at an intensity of ≥75% 1RM, utilizing whole body and free-weight exercises, at altering body compositional measures (ES of 0.47, 0.30, and 0.40 for loss of BM, FM, and retention of FFM respectively)" (Clark. 2015)
Now, while this may still be in line with at least some of the mainstream recommendations, Clark's observation that the RT regimen was also more effective at reducing total cholesterol (ES = 0.85), triglycerides (ES = 0.86) and low-density lipoproteins (ES = 0.60), as well as at reducing fasting insulin levels (ES = 3.5) than endurance training or  endurance training and resistance training in combination emphasizes how much of a game changer (intense!) resistance training can actually be.
Avoid black and white thinking! Despite the fact that the meta-analysis at hand shows on average that interventions that focus on diet + resistance training are the most effective ones. It would be haphazard to conclude that doing a moderate amount of cardio would be counter-productive. If you use it, to eat more, it may in fact impair your results. If you go for a 20-minute jog at a moderate pace thrice per week, though, this is neither going to burn away muscle mass, nor stalling your fat loss. As discussed below, the lack of additional effects of combined training in the meta-analysis at hand may well be caused by factors that have nothing to do with the often-heard-off ill effects of moderate intensity cardio.
Figure 3: The good results some studies on combined training show suggest that the lack of benefits in the meta-analysis may be a statistical phenomenon, or a result of certain aspects of the individual study design (e.g. low volume or intensity) in some of the studies (data from Donnely. 1991).
There's thus just one thing we still have to address: Why is doing both, cardio and resistance training not more effective? Well, the answer may be hidden in the study design, where the combination training rarely complied to the previously outlined rules of a high intensity, progressive, high volume resistance training workout with free weights. In addition studies that met these criteria, such as Cuff et al. (2003), for example, didn't measure the body composition of their female subjects and focused on weight changes, exclusively. In the exceptional studies that had both a sensible resistance training regimen and comprehensive analyses of body composition in place, on the other hand, suggest that the lack of benefits in the combined training analysis of Clark's study may be a statistical phenomenon.
Bottom line: If you still need material to convince your significant other that hitting the weights is not only more time-efficient and less daunting than hours on the treadmill, but also more effective when it comes to improving his/her body composition and/or health, I'd suggest you print this article and pin it on your fridge.

Losing Weight Doesn't Have to Ruin Your Metabolism | more
Eventually, though, the article has another, even more important message than "resistance beats cardio training". Which one? Well, there is "no relationship between any treatments effectiveness for inducing acute changes in energetic balance with the effectiveness for induced responses to body composition or biomarkers of health from said treatment program" (Clark. 2015). A revelation that reinforces the idea that our individual body composition is not a function of energy intakes vs. expenditure. The effects of metabolic stress, which is obviously greater for resistance and HIIT training (compared to steady state, the HIIT studies in the meta-analysis yielded better results, too), on the other hand is still underappreciated by both practitioners and scientists of who James E. Clark is one of the first to conclude that the "focus of treatment should be on producing a large metabolic stress (as induced by RT or high levels of ET [don't overdo it on "cardio", though | learn why]) rather than an energetic imbalance for adults who are overfat" (Clark. 2015) | Comment on Facebook!
References:
  • Clark, James E. "Diet, exercise or diet with exercise: comparing the effectiveness of treatment options for weight-loss and changes in fitness for adults (18–65 years old) who are overfat, or obese; systematic review and meta-analysis." Journal of Diabetes & Metabolic Disorders 14.1 (2015): 31.
  • Cuff, Darcye J., et al. "Effective exercise modality to reduce insulin resistance in women with type 2 diabetes." Diabetes care 26.11 (2003): 2977-2982.
  • Donnelly, Joseph E., et al. "Effects of a very-low-calorie diet and physical-training regimens on body composition and resting metabolic rate in obese females." The American journal of clinical nutrition 54.1 (1991): 56-61.