How Restriction Affects the Brain

A lot of people come to me wanting to improve their eating habits, but what they’re actually asking about is restricting their diets — like wanting to cut out sugar or wanting to eat only particular foods. They want to lose weight. They want to look like the impossibly thin and fit people they see on their screens.This puts me in a tough spot. I want to help my clients reach their goals, but I also know a lot about the unhealthy effects of restriction and how pervasive disordered eating has become in our culture. Anorexia in particular can cause significant damage, and this eating disorder often goes unrecognized even by people with anorexia.

Though it might feel disappointing or discouraging to these clients at first, our initial work together often centers on setting different and healthier goals. But in this age when intermittent fasting is all the rage — and when the negative impacts of calorie restriction aren’t common knowledge — choosing healthy habits can feel more confusing than ever. So let’s dig into what happens to your brain with calorie restriction.

How Your Brain Interprets Dieting‍

It’s estimated that 45 million Americans go on diets every year. Most of these diets ultimately fail, thanks in large part to the brain. Your brain likes to maintain your body weight for survival, just like a thermostat keeps a steady temperature inside your house. This is why your body will fight weight loss, or sometimes even weight gain — regardless of what you’d like your body’s “set point” weight to be.

"It’s no surprise that dieting can leave you — and your brain — more vulnerable to binges and to overall weight gain."

If your weight changes too much, or too quickly, your brain triggers cravings and other behaviors to get you back on what it thinks is the right track. Studies show these “compensatory mechanisms” can be a factor for at least a year following weight loss. Your brain will even trigger a binge to protect your body’s fat stores. It’s no surprise that dieting can leave you — and your brain — more vulnerable to binges and to overall weight gain. The stress of dieting and the experience of ignoring your natural hunger cues results in a higher risk of emotional eating and mindless eating, too.‍

What Happens with Calorie Restriction: It’s Complicated‍

The results of different studies on how calorie restriction affects health and lifespan can appear confusing and even contradictory. The truth is that the impact of restricted eating is complicated. Restricting calories can increase the lifespan of some shorter-lived species like grey mouse lemurs, but those same restrictions also accelerate the loss of the brain’s grey matter. Some studies report that calorie restriction can protect against brain aging, while others find that calorie restriction negatively impacts the cognition performance of rats and the emotional and intellectual function in humans.

Calorie restriction has been shown in short-term human trials to help improve blood pressure, blood sugar, cholesterol levels, and calorie reduction has been seen to slow Alzheimer’s-related changes in mice. There may be memory benefits from calorie restriction for older adults, but many unanswered questions remain — like the impact of prolonged rather than short-term calorie restriction, and whether these same findings will hold in larger studies with more participants.‍

Anorexia & Severe Restriction‍

Not all human brains are the same. There are subtle but significant differences in the brains of people who struggle with anorexia and in those who have recovered. Serotonin pathways are different, as are reward responses, so these people can have trouble experiencing pleasure and worry more about the potential consequences of a reward — like obsessing over the calories in a delicious dessert. 

"Brain damage is a very real potential consequence of an eating disorder."

These differences can be found in response to food stimuli and even to activities like gambling, suggesting that people who have or have recovered from anorexia have difficulty differentiating between positive and negative feedback. Brain damage is a very real potential consequence of an eating disorder. When you’re starving yourself, your brain doesn’t get the nutrients it needs, and reduced heart rate also lowers the amount of oxygen to the brain. Irritability and isolation are additional possibilities, as are difficulties with thinking and setting priorities. It’s unknown if these differences in the brain are present before someone develops anorexia, or if the brain changes are the result of the eating disorder. However, excessive weight loss is known to shrink the brain’s gray matter and also correlates to increased risk of anxiety and depression.  These symptoms, including reduced brain mass, can improve with restorative weight gain, though the severity and duration of the eating disorder are important factors in recovery. In any case, healing the brain takes time and patience.‍

What about Intermittent Fasting?‍

You’ve probably heard intermittent fasting mentioned several thousand times in articles and blog posts, and it’s all over social media. The idea behind intermittent fasting is simple: you restrict your caloric intake for a set period of time, and then eat normally outside of those fasting periods. A popular intermittent fasting structure is “5:2,” which means five days of normal eating and two days of fasting each week. The idea is that these fasting periods prompt the body to burn stored fat for energy, so you lose weight.

Proponents argue that we already experience periods of fasting between dinner one night and breakfast the next morning, and many claim that intermittent fasting is not a diet but a lifestyle for long-term health and weight loss. Some studies indicate that intermittent fasting might help improve cardiovascular health, memory, and mental performance, too, but it’s important to understand that the long-term effects of intermittent fasting have not been adequately studied. There are significant problems with intermittent fasting, beyond the discomfort of hunger and fatigue. For one, it’s far too easy for those “normal eating periods” to turn into regularly scheduled binge eating days, to make up for the fasting periods — which can result not only in weight gain but also disordered eating behaviors. Fasting can trigger headaches and bouts of dizziness and nausea and may be dangerous for people with medical conditions.

"Possibly the most significant problem with intermittent fasting is that it can cultivate an unhealthy relationship with food or even trigger an eating disorder."

Intermittent fasting also doesn’t take into account additional factors, like sleep habits and stress levels, that contribute to weight loss and maintenance.  Possibly the most significant problem with intermittent fasting is that it can cultivate an unhealthy relationship with food or even trigger an eating disorder. When fasting is taken too far, it can result in yo-yo dieting, depression, sleep issues, nutrient deficiency, decreased immunity, and organ damage.‍

What to do instead of restricting‍

Some people are able to reap benefits from caloric restriction and intermittent fasting, but for individuals who are already struggling with food and eating, I believe the risks far outweigh any potential upside. So what do I recommend to my clients instead? Moderation.

"When you adopt an approach of moderation, it means that no foods are off-limits."

When you adopt an approach of moderation, it means that no foods are off-limits. You’re certainly not calorie counting. You’re simply eating as much as your body needs, to the point where you feel satisfied but not uncomfortably full. It’s a practice of balance, and moderation pairs easily with mindful eating — in which you take your time with your meals, paying attention to all five senses as you eat and eliminating the distractions of screens or other stimuli at mealtimes.

It’s also a matter of re-learning your body’s hunger and satiety cues, and becoming more aware of your personal triggers for eating. Are you reaching for that snack because you’re actually hungry and your body needs fuel, or is it because you’re stressed, angry, or bored? Becoming aware of any patterns of emotional eating gives you back control. You can still enjoy your favorite foods and take pleasure from eating, without overdoing it and without regret or shame — and definitely without fasting hunger or feeling painfully stuffed.

Moderation applies not just to food, and can be adopted as a philosophy of living, too. For instance, moderate exercise — moving your body for both fitness and fun, without overdoing it — along with adequate sleep and learning to manage your stress are also important to a healthy lifestyle. Moderation also applies to the expectations you have of yourself. Why did you want to lose weight? What is a healthy goal for your individual body and circumstances, and what are the benefits and risk factors involved when you consider making a change? The truth is that your health isn’t necessarily tied to — or guaranteed by — an unrealistic goal weight. Healthy behaviors are a more constructive focus, and moderation is more likely to support your overall well-being in the end.