A complex array of interacting factors regulates your appetite. The “appetite centers” in your brain consolidate and analyze neurological, hormonal, mechanical and psychological signals, and there your conscious awareness of hunger is born. Scientists investigating America’s obesity epidemic have shed some light on the intricate mechanisms controlling appetite, including the effects of meal timing. Eating late at night can provoke physiologic changes that increase your sense of hunger the following morning.
Your appetite centers are located in the nuclei within your brain stem and hypothalamus. The cells in these areas respond to your blood glucose level, to nerve impulses arising from your gastrointestinal tract, to various hormones, including ghrelin, leptin and thyroid hormones, and to numerous other stimuli. Fluctuations in hormone and blood glucose levels impact your appetite in a predictable fashion. For example, a falling blood glucose level or an increasing ghrelin level stimulates hunger, while rising glucose or leptin levels suppress your appetite. Insulin influences the levels of many other appetite-regulating factors.
Insulin and Appetite
Insulin is a hormone produced by your pancreas in response to consuming a meal. Insulin stimulates the cells in your liver, fat tissue and muscles to absorb glucose and then to burn it for energy or store it for future use. As insulin drives your glucose level downward, your pancreas and adrenal glands produce counter-regulatory hormones, such as glucagon and epinephrine. The appetite centers in your brain are stimulated by falling glucose levels and counter-regulatory hormones, making you feel hungry again. Thus, the more insulin your pancreas produces in response to a given meal, the greater the subsequent rebound in your appetite.
When you eat a meal at bedtime, particularly one rich in sugars and other simple carbohydrates, you generate an insulin surge from your pancreas. Upon retiring, this insulin begins pushing glucose into your cells, a process that continues as you sleep. During the night, a continual drop in your blood glucose stimulates the release of counter-regulatory hormones, leading to stimulation of your appetite centers. Unless you get up in the middle of the night to satisfy your appetite, you will be hungry upon arising in the morning.
The factors that regulate your appetite are not as straightforward as was once believed. The interactions among ghrelin, leptin, insulin, glucose, thyroid hormones, growth hormone and other determinants of hunger or satisfaction are intricate and only partially understood. To confuse matters further, sleep-inducing hormones, such as melatonin, exert their own influences on your appetite, and changes in sleep patterns can alter the way your brain responds to hunger signals. If you are trying to control your weight, the timing and composition of your meals could impact your success; consider consulting a nutrition expert or getting advice from your physician.