There’s a tendency to blame willpower or your mind if a diet becomes difficult to stick to when in reality, your body is simply trying to survive. Here’s what you need to know about your biology.


Every year, millions of people opt to go on a diet for the promise of a newer version of themselves. One of the first questions people usually have when it comes to changing up their eating habits: why can’t I stick to a diet?

Before we get into the answer, we need to dig into the concept of a set range weight theory.

There are several different systems in place throughout your body that helps regulate various biological functions, including breathing rate, body temperature, and blood sugar. They’re called “homeostatic mechanisms”, and their functions are to keep your body at equilibrium around a set range. For example, when you’re in a hot environment, your body sweats to release heat – but when it’s cold, you shiver to produce heat.

Each of us lives in a body that has a preferred weight, similar to a homeostatic mechanism. It’s usually referred to as the “set range weight” or “defended range.” It’s important to refer to this concept as a range, not a point.  There are several estimates for how wide this range is, but it’s likely anywhere between 10-20 pounds.

Your body’s job is to defend this range, i.e., to keep your body at the same relative weight. Contrary to what we’ve been taught, we don’t need to micromanage our body weight – our body does it for us through a complex set of mechanisms. It appears that the bottom of our set range weight is defended more strongly than the top, meaning that we resist weight loss more than we resist weight gain.

So how do you know if you’re in your set range? It’s the weight your body reaches when:

  • You’re not dieting or restricting.
  • You’re moving your body in a joyful, life-enhancing way.
  • You’re providing your body with its energy and pleasure needs through food that nourishes your body and soul.
  • Your brain space and energy are directed towards living our your life and not obsessing over your weight.

So, what happens when we diet and attempt to push our body weight below our set range weight?

First, it’s important that we clarify that diet can technically mean either “eating pattern” or “attempt at weight loss”. However, most people are familiar with the latter through conscious attempts to lose weight, restriction of calories, and elimination of whole food groups.

During this period, people are often on a recurring “diet-binge” cycle, and why diets set us up for failure and keep us in a perpetual rhythm of dieting.

We begin a diet due to a trigger, whether that’s an ad, a magazine article, a friend telling a “success story,” a doctor making comments, a celebrity testimony, or another event. We cut out calories or food groups, decide on a “clean eating” pattern, or track food on an app.

In the background, our body is panicking due to underfeeding. It increases stress hormones, hunger hormones, and fat storage hormones. It decreases fullness-producing hormones to protect us from starvation. Eventually, we become more and more preoccupied with food, and our body’s cues begin to outweigh our self-imposed diet rules. We eat, and feel like failures for doing so.

So we resolve to start another diet, and try harder this time.

This perpetual binge-shame point of the cycle is a problem, especially as we believe that with more willpower, we can successfully stick to a diet. However, the willpower argument fails to acknowledge the several physiological systems we have in place that override our will to diet. These side effects of dieting include:

So let’s go back to the original question: why can’t you stick to a diet? You’re not designed to.

Your body is too smart to let you intentionally underfeed it – and while it can’t tell the difference between intentional restriction and starvation, it has protective mechanisms in place to avoid the former. However, unlike with medications, we’re not typically warned of the side effects of diets before they are prescribed.

We have been brought up in a culture that values specific body sizes and shapes, views body size as controllable, and sees anyone in a different body size as less-than or lacking willpower If this environment of fatphobia and weight stigma has left you feeling skeptical or doubtful of this information, that’s okay.   You may have been hoping for answers and a quick solution to why you can’t stick to a diet,

But the real answer lies in recognizing that diets aren’t a prerequisite for health.

Adapted from the original article.

Amy Hanneke, RDN, LD is a Registered Dietitian and owner of Satisfy Nutrition.  Through an anti-diet approach in her nutrition coaching practice, Amy firmly believes in helping individuals live a life without restrictions, full of joy, self care, and delicious food. Learn more about Amy at Satisfy Nutrition.