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7 Major Reasons Diets Don’t Work

Updated: Jan 5

Written by: Natalie Faella, MS, RDN, LDN | August 25, 2021

young woman with long blonde hair unsure of what to eat in the fridge; fad diets posted on refrigerator; unsure of what to eat and how to follow diet

Let’s face it, we’ve all had those moments of “I have to stop eating X, Y, and Z” or “I’m only having salads this week.” Typically this may happen after a fun vacation’s worth of meals and drinks, or scrolling past an exceptionally slender and toned Instagram model’s posts. It's as if we think we're one new diet trend away from feeling better, looking better, and being better. The pressure to look or eat a certain way is REAL. This probably has something to do with why the diet industry is a billion-dollar industry. That, and the fact that diets are actually designed to fail.


Think about it — do you know anyone who’s successfully been on a restrictive diet for years?


What about your own experiences? Have you ever tried to cut something out of your diet (bread, sweets, fats) and noticed once you reintroduced it, any weight that was lost came right back on? Or maybe you started craving the foods you cut out and ended up overindulging when you allowed yourself to take a “break” the diet? This isn’t because you failed at dieting; the act of making a food forbidden actually increases the allure of it until there is permission to eat it. It’s part of the vicious dieting cycle where we cut out foods, feel guilt when we eat them, swear to never eat them again, then crave and overeat them over and over again.


Or how about when you're following a diet and all of a sudden the weight isn’t coming off as fast anymore or just totally stops (that “plateau” in weight loss dieters often experience)? Or when you finally ditch the diet and then eventually notice your weight is higher than before you started?


This is because dieting itself is actually one of the greatest predictors for future weight gain. Yup — read that again! This is especially the case in repeat dieters and those that started dieting when they were younger and in leaner bodies. This increase in weight eventually leads us to try another diet, and another diet — a cycle known as yo-yo dieting, which leads to weight-cycling.


There are several reasons for weight-cycling, AKA reasons why diets don’t work. Here are some of them:


1. Dieting slows our metabolism.

Our metabolism, or basal metabolic rate (BMR), is the rate at which our body uses/burns energy (i.e., calories) to perform normal daily functions like breathing, digesting, etc. This burn rate actually decreases as a result of calorie restriction and weight loss. When we restrict intake below our nutrient needs, the body goes into starvation mode, meaning it conserves the calories we take in instead of burning them at our usual rate to perform its daily functions. The body essentially does this because we’ve given it the impression that we do not have access to enough calories to meet our needs; or in other words, it thinks we're experiencing a famine. While it is amazing our bodies are able to do this to try to keep us alive during times of starvation, this slowed metabolism is obviously an unwanted result for dieters. A slowed metabolism contributes to that "plateau" in weight loss we see during a diet and the weight gain that results after dieting.


2. Dieting promotes body fat storage.

This is a side effect of the “starvation mode” that results from dieting as well. Instead of using the calories we’re taking in for energy to efficiently carry out body processes, the body prefers to store energy in the form of fat cells in an attempt to keep us alive during this self-induced famine. After we stop dieting, our body may remain in this fat-favoring state for some time. Some of the impaired body functions from lack of energy intake can have consequences on our weight as well. For example, if we don't have enough energy to convert the thyroid hormone to its active form, our thyroid can become sluggish, which makes our metabolism sluggish as well. (And metabolic rate is just ONE of the many things our thyroid plays a role in).


3. Diets increase our set point.

Set point is the weight range where our bodies want to be — where we operate best and can maintain easily without drastic eating and exercise habits. When our weight drops below our set point, our body will actually try to get us back to the weight (or higher) through mechanisms like those mentioned in #1 and #2. We can think of it like a thermostat and how it turns on the heat if the temperature drops below where it is set to be. So not only will dieting prompt our body to get us back to our set point, it can actually increase our set point range, meaning it becomes easier for our bodies to maintain or default at a higher weight than the weight we were before dieting. This is another reason why dieting is one of the greatest predictors of weight gain. (More on set point here).


4. Diets are unsustainable long-term.

As previously mentioned, diets were not designed to be successful or sustainable. No matter how much willpower you have. At some point you are going to want to eat the foods you've been cutting out (seriously, who could give up bread forever?!), eat outside the hours of your intermittent fasting, or realize you don't actually like putting butter in your coffee. Diets are typically designed to be short-term yet for some reason promise (unachievable) long-term results.


5. Restrictive eating and food rules lead to overeating.

Restricting calorie intake below our needs and only “allowing” ourselves certain foods will lead to an obsession with food (this is considered a result of a scarcity mindset). Having food rules (i.e., good vs. bad, can eat vs. can't eat) can also lead to eating in ways to reward or punish our behavior. Have you ever kept thinking about something yummy in the fridge until you finally just allowed yourself to eat it? Or felt like you were “good all week” so now you can really indulge in something? This is how both preoccupation and rewarding one’s self with food can lead to overeating. They can also lead to the development of a serious eating disorder.


6. Dieting can decrease self-esteem.

When we get to that point where weight has plateaued, or we can no longer sustain the strict rules of the diet (like “juicing” instead of eating at lunch), it’s easy to get down on ourselves. We feel like we failed — not knowing that the diet itself wasn’t designed to be effective or sustainable long-term. These feelings of low self-esteem can do a lot of harm. And in terms of impacting our weight, lower self-esteem can make us want to isolate and skip that walk or gym session with a friend, turn to emotional eating for comfort, and/or think "what's the point?" and ditch our healthy lifestyle habits altogether.


7. Dieting impacts our hunger and fullness cues.

When we’re following rules about what to eat, and even when to eat with some diets (I see you, intermittent fasting!), we get out of touch with our hunger and fullness cues. We also start going against our food preferences — eating what we “should” and avoiding what we “shouldn’t” eat, or in other words, not eating intuitively. Both can harm our relationship with food and actually lead to overeating and weight-cycling.


Weight cycling is an inevitable side effect of dieting that is not only frustrating but bad for our health. Weight cycling has been shown to potentially increase blood pressure, insulin resistance (a symptom of Type 2 Diabetes), and cholesterol levels. It can also increase inflammation in the body, which is a risk factor for many diseases like heart disease and diabetes. That’s right, dieting can actually lead to the diseases that weight loss is often prescribed to improve or prevent!


With the increasing societal pressures and messages about “the war on obesity,” it's important to recognize that dieting may not be the answer. The focus instead should be on encouraging lifestyle practices that support or improve overall health and well-being (like joyful movement and intuitive eating), as that pressure for a particular number on the scale can actually cause more harm than good.


If you can relate to weight-cycling, yo-yo dieting, or any of the physical or emotional tolls of dieting, I encourage you to ditch the diet approach. The real “perfect” diet is the one that comes naturally to you by listening to your hunger, fullness, preferences, feelings, cravings (yes, even cravings!), etc.


Stay tuned to learn more about my anti-diet approach to nutrition, health, and wellness by subscribing here!

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