It’s fascinating how our body systems are so complex. Weight gain, for example, can be seen as a consequence of taking in more calories than the body’s use of calories. However, could there be more to weight gain and weight loss than calories and the body’s metabolism? The answer is YES. There are various body systems and hormones involved in weight fluctuation. As a result, factors such as stress can indirectly cause weight gain.
It is true that the root cause of weight gain and loss is calorie intake. Our bodies naturally use the food taken in as an energy source for important functions in the body. Despite having minimal movements throughout the day, we can still be using up calories. Resting Metabolic Rate or RMR is the amount of energy that the body uses to maintain or carry out necessary body processes(1). Even when we are least cognizant of it, our bodies are using energy. One’s resting metabolic rate is unique to him or her. There are factors such as gender, height, body mass, and age that shape one’s metabolic rate. These factors shape how well your body is able to break down food and turn it into energy.
Therefore, when one has a calorie intake that is less than their expenditure of energy, he or she is likely to lose weight. This fact is the reason why so many diets are able to help people lose weight: The diets help cut down calories intake. However, more often than not, people that lose weight often feel extra hungry (2). It seems that individuals gain weight quickly right after they finish a diet or lose a significant amount of weight. How can this be?
Usually, weight regain is caused by hormones. There are various hormones that indirectly cause weight gain. They do this by increasing your appetite to eat. For instance, leptin and ghrelin are antagonistic hormones that affect one’s appetite. Antagonistic hormones are hormones that have opposite effects on the body. Leptin is a hormone that is secreted by fat cells and decreases the appetite. The hormone sends signals to the brain that notify it that there is enough fat stored in the body. Contrarily, ghrelin is a hormone that increases the appetite. Research suggests that ghrelin is released by the stomach and transmits signals to the brain (3). These signals give us feelings of hunger and prompt us to eat. When an individual under eats, their ghrelin levels oftentimes increases. As a result, their appetite becomes higher than it was originally.
Still, individuals with more fat cells in their body do not necessarily have a lower appetite although they have higher levels of leptin. It is believed that some individuals resist some of the appetite-suppressing effects of the leptin in their body (4). On the same note, avoiding fatty foods helps people lose weight, not the opposite way around. People are urged to have a healthy balance of their “hunger hormones” by getting an adequate amount of sleep. Sleep deprivation or a lack of sleep increases ghrelin levels.
As complex as the body is, there are many other hormones that send varying signals to the brain to stimulate the appetite. For instance, the hormone cortisol is secreted by the adrenal glands (5). Many people associate cortisol as the stress hormone because it is released as a response to spiking stress levels. When the hormone is released, an individual has an increased appetite. Other factors, such as low-calorie intake, can cause higher levels of cortisol. Another hormone, neuropeptide y can also increase one’s appetite. Neuropeptide Y is created and secreted by the cells in the brain and the nervous system. The hormone is often released in higher amounts as a result of low-calorie intake (food-deprivation) or rising stress levels. Upon release, the hormone causes the body to crave carbohydrates. There are many other hormones in the body that also contribute to weight fluctuation and appetite levels.
All goes to show that there are many variables to consider when attempting to make sense of weight fluctuation or gain/lose weight. It is even more fascinating that hormones and metabolism are also not the only factors that contribute to weight gain and loss. These are just two snippets of what can cause weight fluctuation. Hopefully, these snippets will help you understand your increased appetite after a big diet or a stressful week!
References and Footnotes
- Pritikin. “Pritikin.com.” Pritikin Weight Loss Resort, 18 Aug. 2018, http://www.pritikin.com/what-is-resting-metabolic-rate.
- Goodman, Brenda. “Research Sheds Light on Why People Who Lose Weight Gain It Back.” WebMD, WebMD, 14 Oct. 2016, http://www.webmd.com/diet/news/20161014/how-your-appetite-can-sabotage-weight-loss#1.
- Magee, Elaine. “Your ‘Hunger Hormones’.” WebMD, WebMD, http://www.webmd.com/diet/features/your-hunger-hormones#1.
- “9 Proven Ways to Fix The Hormones That Control Your Weight.” Healthline, Healthline Media, http://www.healthline.com/nutrition/9-fixes-for-weight-hormones#section2.
- The adrenal glands are located on top of each kidney.