Diets don't work because caloric restriction is difficult to maintain.

If you’ve ever tried dieting, you may be wondering why diets just don’t work. Find out why diets set you up to fail, and what you can do instead!

For people looking to lose weight or feel and look healthier, diets seem to be the go-to solution.

But somehow, despite New Year’s resolutions, despite so many different popular diet options claiming to give you the results you want, roughly 90% of diets fail in the long term.

Wait, what? 90%?!

Why does almost everyone who starts a diet fail to continue or see long-term results?

Is there something inherently wrong with dieting?

Let’s dive into why diets don’t work, who should/shouldn’t diet, and the best dieting alternatives.

Why do Diets Fail?

Diets don’t work because they are a short-term solution.

Dieting consists of caloric restriction, typically with the end goal of losing weight.

Every new diet has something that they claim is the secret ingredient that makes it successful – the one thing every other diet is missing. Usually one specific macronutrient (carbs, fat, etc.) is focused on as the way to reduce calories.

But when it comes down to it, all weight loss diets boil down to one thing: calorie deficit.

If you burn more calories than you consume, you will lose weight.

This means diets are intrinsically restrictive. And this is what makes them so hard to win at.

Studies have shown that dieting can work for weight loss in the short term, but not in the long term (1, 2).

The problem in the long run is that, once the diet is over, individuals tend to gain back whatever weight they worked so hard to lose, over the next few years. And often, these individuals will in fact gain even more weight than they had before dieting.

What Causes Weight Regain?

First of all, evolution is not on your side.

We evolved in an environment where food was scarce, so we are hardwired to preserve body weight and resist any weight loss.

Your body is not going to let you starve and will do everything it can to maintain a constant weight.

This scientific review goes over the biological adaptations that occur in response to dieting.

Basically, the body resides at a “steady state” weight. This is the weight that your body will gravitate towards and will not want to budge from. This weight is determined by a combination of genetic, environmental, behavioural, and homeostatic pressures.

When you start dieting, the reduced caloric intake induces the initial drop in weight as your body burns through glycogen, fat and muscle stores for energy.

However, as you lose weight, your homeostatic system gets to works slowing your metabolism and making you feel hungry in order to adapt to, and counter, the dietary change. Eventually, it will establish a new, lower steady state weight. This is where the common plateau in weight loss occurs.

At this point, to maintain that new, lower weight, you must maintain your diet. To lose even more weight, you will need to intensify your diet.

Unfortunately, restrictive diets are difficult to maintain long-term, so weight regain is typical.

Mechanisms of Diet Failure and Weight Regain

Part of what makes dieting feel impossible and miserable, is the overwhelming desire to eat more.

When dieting, certain hormones kick in to tell your body that you are hungry and you need to eat more.

Hormones that stimulate hunger, such as ghrelin, are increased, and hormones that suppress hunger such as GLP-1 and leptin, are decreased (3).

The result of these hunger cues is increased hunger and appetite, likely followed by increased food intake and weight gain.

What’s more, these hormonal changes in response to dieting are not a temporary response. Hormone levels have actually been shown to remain increased or decreased one year after the initial dieting (4).

This explains why weight gain is favoured after dieting – the intense hunger cues don’t really turn off, even when you have stopped dieting and are eating your usual amount of calories, which causes you to start eating more.

Leptin, thyroid hormones, and other hormones can also control energy expenditure. Reducing your food intake will cause your body to increase energy conservation. As you lose weight, you lose muscle, and so your energy requirements decrease and your metabolism will consequently slow down.

Furthermore, your energy expenditure goes down when body mass is decreased. Less energy/calories will be burned after weight loss with the same physical activity as before weight loss, due to the decrease in total body mass.

Weight regain may also in part be because of increased stress and cortisol levels that result from dieting (5).

When do Diets Succeed?

When you stick to it! No matter the diet.

Again, weight loss will only occur as long as you can maintain a calorie deficit.

To Diet or Not to Diet?

Here are a few scenarios:

If you need to go on a specific diet because of a health condition, then you gotta do what you gotta do. Your health condition and your doctor’s advice should help you make the dietary changes you need to make.

If you are dieting because you want to lose weight and get fit, and your attempts at typical dieting are not working, try some of the steps below.

3 Things to do Instead of Dieting:

1. Start with the right mindset

It is important to have realistic expectations when it comes to making a dietary or any other kind of change.

Any change in eating habits, weight, physique, etc. is going to take time.

Don’t go in thinking this is a quick fix and then it’s over – I’ll suffer for a bit and then reap the rewards forever after. It’s not, and you won’t.

The problem with most diets is that they are treated as a temporary thing. While this may work for people who just want to lose weight quick before their wedding day or vacation, most people are not okay with watching their hard work slip away as they regain weight once the diet is over.

Instead, go in thinking that this is going to be a healthier lifestyle that you are going to transition to, that will make you feel better and help you achieve your goals each and every day.

This approach is going to take time and adjustment.

But remember, it is long-term success that you want.

2. Incorporate small habit changes into your life

In order for something (i.e. weight loss) to be sustainable, it needs to become a habit and a lifestyle.

Do you really want to be living your life worried about what you are or aren’t allowing yourself to eat?

Wouldn’t it be so much nicer if you can find a lifestyle that works for you, that you naturally follow without even trying, and that gives you the lasting results you want?

After all, the reason you may turn to dieting is because your current habits are not benefitting your health. So make the shift to a lifestyle full of habits that will benefit your health.

Healthy habits could include drinking your morning coffee without two spoons of sugar, or keeping a water bottle on hand at work, or swapping fast foods for simple whole foods.

It’s definitely not easy to change a habit, but honestly, it’s probably a whole lot easier than dieting.

Something like replacing your favourite sugary snack with a healthier option can be tough in the beginning, but you get used to it. Once it becomes a habit, you will be making that healthy choice without actively thinking about it or having to muster up your will power.

Compare this to a restrictive diet where you’re saying no snacks at all…all you’d ever be able to think of is when your next cheat day is!

The best part is, accomplishing goals, no matter how small, is a very strong motivating force to accomplish even more goals. Your small habit changes and health improvements will continue to snowball and encourage and enable you to improve your health further.

3. Focus on the right things

Improving your health comes down to 3 main things: diet, exercise, and sleep.

Diet: establish balanced and clean eating habits. By avoiding highly sugary and processed foods (aka empty calories), you will cut down on calories while fueling your body with nutrient-rich alternatives.

Give some of these habits a try:

  • cut down on added sugar
  • replace processed foods with whole foods
  • cook at home instead of eating out or ordering in
  • meal prep

Exercise: schedule in at least 150 minutes of physical activity a week. If you’re focused on weight loss, make a plan to slowly increase the amount of time you exercise each week/month. Remember, cutting calories alone won’t do it because your metabolism will slow and so you need to be burning more calories as well. The more muscle mass you develop, the faster your metabolism will be.

Give some of these habits a try:

  • go for a walk every day such as before or after work
  • reduce sitting time, or break it up with a quick walk, stretch, or flight of stairs
  • lift some weights
  • take up a new activity/sport

Sleep: if you are not sleeping enough (7-8 hours), the rest is meaningless.


Weight loss occurs when you burn more calories than you consume. However, calorie-restrictive dieting is unsustainable and weight regain will occur once dieting is over. Instead of dieting, try incorporating small, sustainable changes into your daily food, exercise, and sleep habits.

I hope you found this article on why diets don’t work and what to do instead, helpful! If you enjoyed this article or have any questions, be sure to comment down below!

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