For those of us who have tried dieting, the experience of rebounding weight gain is all too common. Dieting typically comes with an insatiable hunger that often leaves us wondering: “Why am I constantly hungry?”

Your genetic expression can make feel hungry all the time

The article on Epigenetics of Nutrition explained the mechanism by which our environment influences epigenetic changes in our DNA. The composition of nutrients in diet can work to activate and deactivate genes in our DNA at the molecular level. It can influence the activities of enzymes, and it can even turn off genes that promote aging.

It makes sense from an evolutionary viewpoint that intermittent fasting would prolong life. Our ancestors survived famines and long-term food shortages by epigenetic changes that promoted longer lifespan and retarded their reproductive systems.

The genetic expression of aging genes is not only related to epigenetic modifications. It works across generations when natural evolutionary forces decide who survives and who does not. When food is abundant, natural selection favors fertile women with shorter lifespans. When food is scarce, natural selection favors women with longer lifespans.

As James Holland Jones put it: “High fertility increases the selective premium placed on early survivorship, while high life expectancy at birth decreases it.”

Poverty and Obesity

As Gary Taubes repeatedly points out in his book, The Diet Delusion, obesity is most common amongst the poorest in society. Moreover, evidence shows that this group does not have a sedentary lifestyle as the medical establishment claims. This demographic carries the burden of physical labor for the rest of society.

This was first documented in 1965 in a study by Albert Stunkard that found obese women to be six times more common at the lowest socioeconomic level than the highest. Many studies around the world have confirmed the same link between poverty and obesity.

Again, this has nothing to do with metabolism or a sedentary lifestyle and everything to do with the prevalence of low-nutrient high-carbohydrate diet amongst the poor that puts them in a perpetual state of malnutrition. The rich are more likely to consume fish, meat and a variety of quality vegetables.

Your early life epigenetic changes make you binge on food

In his TEDx talk (video linked above), Moshe Szyf tells us how our gene expression changes by exposure to environmental factors. Moshe describes the biochemical processes by which genes can be turned on and off early in childhood.

Excerpts from transcript of Moshe’s speech

05:03 So, what we suggest is perhaps what happens early in life, those signals that come through the mother tell the child what kind of social world you are going to be living in.

05:14 “Is it going to be harsh and you better be anxious and be stressful? Or is it going to be an easy world and you have to be different? Is it going to be a world with a lot of light or a little light? Is it going to be a world with a lot of food or a little food?”

05:28 “If there’s no food around, you better develop your brain to binge whenever you see a meal or store every piece of food that you have as fat.”

05:54 “For example, if you’re born to a poor family and the signals are ‘You better binge, you better eat every piece of food you’re going to encounter.'”

06:22 “The same preparation that was supposed to protect us from hunger and famine is going to cause obesity, cardiovascular problems, and metabolic disease.”

07:05 “So, geneticists will try to tell you that poor people are poor because their genes made them poor.”

07:10 “Epigeneticists will tell you poor people are in a bad environment,  or impoverished environment that creates that phenotype, that property.”

Thrifty Metabolism

From an evolutionary perspective, it makes sense why our bodies respond to reduced dietary sources of energy by lowering our metabolic rate immediately. It also makes sense for the survival of our species that any subsequent increase in the energy intake will only raise the rate of metabolism back to the original levels after a longer period of adaptation.

Weight gain due to hormonal imbalance

When our ancestors were undernourished, their bodies adapted by becoming more efficient at consuming every available calorie. The mechanism by which this works is a hormone called insulin. During a fasting or a low-calorie period, insulin sensitivity is increased. This is a desired outcome for the purpose if increasing longevity. The consequence, however, is that cellular insulin receptors become highly sensitive to the reintroduction of carbohydrates in the diet.

As dietary sources of energy decrease, the level of thyroid hormone also drops. The thyroid hormone regulates metabolic activities, and it increases basal metabolic rate. When food is scarce, thyroid activity is reduced, oxygen consumption goes down, and ATP hydrolysis is reduced.

It is somewhat contradictory to accept that it is possible for a pregnant woman to fatten and put on weight by hormonal changes even if she maintains the same level of calorie intake, and yet we blame people who cannot control their homeostatic weight on willpower. Sadly, the advice given to the victims of obesity is to exercise and go on semi-starvation diets, which ultimately fail as soon as they are abandoned. Most cases of obesity are better addressed by targeting low insulin levels.

Why you are always hungry after caloric restriction

The homeostatic system in humans evolved to balance energy intake and expenditure and maintain a stable body weight over time. When dietary fuel is limited, the body switches to consuming its fat stores. The reverse process, however, does not work so smoothly with modern food. The proliferation of refined carbohydrates in our food supply made this balancing mechanism malfunction in favor of fast weight gain.

Carbohydrates trigger an insulin response because glucose in the blood is toxic beyond a certain point. This threshold is easily breached with refined carbohydrates. The insulin spike signals muscle and fat cells to store ingested glucose and fat. You feel hungry again because the liver is no longer breaking down fat, and glucose is depleted in favor of storage.

Our paleolithic ancestors evolved to consume calories in the form of fat. Carbohydrates in the human diet are a relatively recent phenomenon. The main reason why we remain hungry while we continue to put on weight is the increased allocation of our modern diet to energy sources from carbohydrates vs fats.

Simply put: it is not the overall calorie count that matters, but the distribution of the macronutrients providing those calories.

Your sleep patterns are disrupted

Your internal circadian clock governs when you get hungry. Research has shown that circadian rhythms actually regulate hunger such that it peaks right before sleep. This increase in appetite promotes larger meals before the fasting period during sleep. This timing also makes sense from a hormonal perspective because the activation of metabolic processes induces a feeling of fatigue.

By morning, hunger disappears, which is why our breakfasts are much smaller, with many people opting to skip the morning meal altogether.

If sleep patterns are disrupted, the circadian rhythm that governs hunger is also disrupted. This is one of the reasons you may feel hungry all the time instead of at the strategically important feeding time before sleep.


Gluckman, Peter D et al. “How Evolutionary Principles Improve the Understanding of Human Health and Disease.” Evolutionary Applications 4.2 (2011): 249–263. PMC. Web. 6 Dec. 2017.

Jones, James Holland. “The Force of Selection on the Human Life Cycle.” Evolution and human behavior : official journal of the Human Behavior and Evolution Society 30.5 (2009): 305–314. PMC. Web. 6 Dec. 2017.

Rogers, P.J. and Brunstrom, J.M. Appetite and energy balancing. Physiol. Behav. 2016; 164: 465–471.

Scheer, Frank A.J.L., Christopher J. Morris, and Steven A. Shea. “The Internal Circadian Clock Increases Hunger and Appetite in the Evening Independent of Food Intake and Other Behaviors.” Obesity (Silver Spring, Md.) 21.3 (2013): 421–423. PMC. Web. 6 Dec. 2017.

Taubes, Gary. 2009. The Diet Delusion [Kindle version].