What actually happens to your body when you diet?

If you ask anyone what happens to your body when you diet, most people would say “duh, you lose weight!”

Most of us grew up believing weight loss was simple. Eat less, move more, the weight comes off. If it didn’t work, it was a you problem.

But that story leaves out almost everything that actually happens inside your body. When you understand the biology, struggling with dieting stops looking like a character flaw and starts looking like exactly what it is: a predictable physiological response.

Let’s go over what actually happens to your body when you diet, both psychologically and physiologically.

What is the calories in, calories out framework?

The calories in, calories out framework treats weight loss like math. Eat 1,200 calories a day for a few months, lose the weight, go back to normal.

Or maybe you convince yourself you’ll just live like this forever and when you can’t, you assume something is wrong with you.

This framing makes dieting seem like a simple equation and puts all the blame on the person doing the dieting. It ignores the fact that your body has a lot to say about all of this.

What happens to your hormones when you restrict calories?

The moment you start restricting, your body adapts hormonally.

Leptin is the hormone that signals fullness to your brain and falls rapidly in response to fasting and severe calorie restriction. This means your brain is getting quieter and quieter signals that you’ve had enough to eat. At the same time, caloric restriction and weight loss induce significant increases in ghrelin, a potent hunger-driving hormone.

You are simultaneously getting louder signals to eat and weaker signals to stop. These hormonal changes help explain the compensatory increase in appetite that contributes to the poor long-term maintenance of weight loss from calorie restriction.

This isn’t a motivation problem. It’s your body doing exactly what it was designed to do: protect you from starvation.

Can dieting lead to food noise?

While there are a lot of factors at play, dieting seems to be associated with an increase in food noise.

One of the best examples of this comes from the Minnesota Starvation Experiment. 36 healthy male participants went through a 24-week starvation phase that caused each to lose an average of 25% of their body weight.

The men dreamed about food, fantasized about high-calorie items they couldn’t access, spent much of their time talking about food, and became agitated if the timing of meals was changed or a meal was delayed. Participants became far more preoccupied with food, which became a focal point in conversations, and some volunteers struggled to concentrate due to this preoccupation. Their interest in food expanded into reading cookbooks and collecting recipes.

Research shows that restrictive eating disorders are also associated with increased food noise. However, the extent of this can vary from person to person. This is complex! It would make sense that the degree of food noise with restriction is related to genetics, degree of weight loss, and motivation for restriction (weight versus religious observance).

More research needs to be done on this topic. However, it is very clear that an increase in food preoccupation when chronically dieting is most likely related to biology versus a personal flaw.

What are the physical effects of prolonged calorie restriction?

Extended restriction has real consequences that rarely make it into the diet culture conversation.

The Minnesota Starvation Experiment as well as research done on eating disorders and chronic dieting show many physical side effects:

Low blood pressure and heart rate that can lead to heart failure
Depleted electrolytes leading to irregular heartbeats, heart failure, seizures, and muscle cramps
GI issues: slowed gastric emptying, constipation, nausea, diarrhea, etc
Brain fog, dizziness, fainting
Difficulty regulating body temperature
Numbness and tingling in extremities
Low sex hormones and thyroid hormones
Bone loss and high risk of bone fractures
Low sex drive
High cholesterol
Dry skin and brittle hair
Kidney failure
Anxiety and depression
Anemia
Increased risk of getting sick

While many of these side effects are more common with extreme restriction, dieting comes with a slew of consequences (brain fog, binge eating, hormone dysregulation, anxiety, depression, decrease metabolism). Dieting also comes with an increased with of this developing into something more severe.

Society paints restriction as consequence-free, even virtuous. The reality is: you need to consider the side effects of dieting and whether it’s actually worth it. Especially when you can improve your health without focusing on restriction.

Why does dieting lead to binge eating?

Not everyone who diets will develop a clinical eating disorder. But chronic restriction puts a lot of people on a restrict, binge, repeat cycle that can quietly shrink their lives.

Restriction frequently leads to preoccupation with eating, dysregulated hunger/fullness hormones, binge cycles, and emotional distress. Social experiences get filtered through what you can or can’t eat. Mental energy gets redirected toward food rules instead of the things you actually care about.

That’s a predictable outcome of treating your body like a math equation..

Now that you know what actually happens to your body when you diet, what’s the alternative?

Understanding why dieting is hard doesn’t mean giving up on taking care of yourself.

When you stop blaming yourself for a biological response, you can start asking better questions. Not “why can’t I stick to this?” but “what does my body actually need?”

When we focus on what we can ADD to our diet, it leaves us feeling empowered and not deprived. We can slowly improve our health by adding more fiber, color, protein, healthy fats, etc regardless of the fun foods we still enjoy. We can eat consistently during the day with a variety of nutrients that promote blood sugar balance, energy levels, and satisfaction. Choosing food no longer is a mental battle or guilt trip.

Now that you understand what happens to your body when you diet, are you ready to try something else You can work with an anti-diet registered dietitian here to ditch dieting and heal your relationship with food! They will help you debunk beliefs about food and establish habits that will improve your health without shrinking your life.