This Is What Happens to Your Brain on a Diet

Updated: Mar. 08, 2021

Your body and brain naturally fight against dieting. But that doesn't mean you can't diet healthily and sustainably.

There are countless dieting tips, tricks, recipes, and meal plans you can find in a single Google search, all promoting different ways to lose weight. But what you eat—and how much—is affected by more than just your hunger, desire to control eating, or diet plan.

The first thing to understand when you want to lose a few pounds is something experts call your set-point weight: This is your body’s “happy weight”—it’s a size that your brain and body try to maintain, and it includes the fat stores on your belly and elsewhere. According to registered dietitian Dara Dirhan, this amount of fat becomes what the brain has determined to be the best for optimal function. Two hunger hormones are responsible for trying to regulate your body’s set point: ghrelin and leptin, says Dirhan. Ghrelin is known as the “hunger hormone” because it is secreted when the brain senses that available energy stores are running low. This hormone generates feelings of hunger that convince you it’s time to get some food in your belly. Your digestive system converts the calories to blood sugar (glucose), which can then power muscles, organs, the brain, and other cellular functions. Leptin is known as the “satiety hormone”—it’s released when your body senses that you’ve eaten enough; it signals the brain that energy levels have been met.

These signals have three primary functions, according to David Prologo, MD, a dual board-certified obesity-medicine physician, and interventional radiologist. They tell your body when to seek food, when to slow down and conserve energy, and when to store and preserve fuel if it senses deprivation (a leftover from the days when famines weren’t uncommon)—and this is all in the name of survival. The brain isn’t concerned with how you look, Dr. Prolongo says. “It is concerned with maintaining life.” Your body and brain are programmed to remain stable at your set point.

How your brain changes on a diet

When you first start a new diet—or you aren’t consuming enough energy for your brain’s needs—you can experience symptoms like weakness, hunger, depression, fatigue, and headaches, among other symptoms. The good news is that after several weeks the brain eases up on these signals, Dr. Prologo says, as your body begins to find a new set point.

Jason McKeown, MD, neurologist, adds that once your body reaches a new set point, you’ll see a reduction in your appetite and cravings. “To maintain results, diets in the long-term can influence this set-range, making your brain adapt and be comfortable at a lower weight,” Dr. McKeown says. It’s also possible to drive your set point upwards, he warns.

Get a new set point

Changing your set point is no easy task: It can take months and sometimes even years, says Dr. McKeown, which is why you should set long-term diet and weight goals. “In the long run you could reset the weight range that your brain has established which will cause your body to speed up metabolism and decrease appetite, becoming comfortable with a lower weight,” Dr. McKeown says. “Whereas in the short run, you may lose a few pounds, but you’ll often plateau and see the weight creep back up as it’s not enough to influence the weight your brain and body is happy with.”

Food quality makes a difference

The quality of your diet is another variable. For brain health and well-being, Dirham recommends choosing a whole foods diet as much as possible. This means staying away from foods that have been processed or refined—energy-dense, high-calorie foods—and incorporating healthier whole foods like fresh fruits and vegetables, lean meat, poultry, fish, and whole grains, Dirhan says. Instead of focusing on what she calls a “calorie salary,” stick to a whole food diet and practice mindful eating (slowing down your eating and taking time to appreciate meals). “This will make sure the brain is happy while aiding in weight loss,” she says. (Focusing on calories is just one of many things keeping you from losing weight.)

Farrah Hauke, a psychologist in Scottsdale, Arizona who specializes in weight management and weight loss, believes that people are more likely to binge when they overly restricting what they eat. When people eat foods higher in fat or sugar, the brain releases “feel-good” chemicals that make the indulgence more rewarding. “We don’t see this same brain stimulation with foods such as broccoli and grilled chicken breast,” Hauke says.

Re-train your brain

When you diet, you can lose out on those feel-good chemicals, which means you’re less likely to get those brain-boosting rewards from dieting. Hauke recommends you find other ways to reward yourself and feel satisfied; the goal is to avoid what she calls “cognitive distortions”—negative thinking patterns that contribute to the common all-or-nothing diet approach.

The experts all agree that rigid rules, unrealistic expectations about eating, and fad diets aren’t the best strategies for your body and brain. Instead, focus on the quality of your diet, listening to your body’s hunger cues, and adding in physical activity. This, along with these tiny changes, can help you lose weight. Research in the New England Journal of Medicine found that intensive lifestyle intervention with health coaches, tailored to the health literacy level of the population, was more effective than usual care.