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.
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).

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.
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.