Allison Kelly Ph.D., C.Psych

All About Attitude

Why Do Dieters Fail?

The reason is more intuitive than you think.

Posted Feb 11, 2020

This post was written by Allison C. Kelly, Ph.D., and Aleece Katan, B.Sc.

Many of us feel dissatisfied with our bodies, especially when we see thin, attractive people. Indeed, a quick scroll through celebrity posts on Instagram can make fad diets seem like the path to happiness. A little willpower for a little while, and maybe we too will feel beautiful. After all, cutting sugar and reducing carbs essentially guarantees that the fat will fall off us, right?

Maybe you’ve tried this out, excited about potential results and the self-discipline you’ll show in the process. “I don’t need bread; lettuce buns are just as good!” “Who needs chocolate when you’ve got gum?” “Pasta is overrated; zucchini noodles here I come!” Within a week, you’ve lost some weight, and your clothes are fitting a bit looser. It didn’t even feel that hard to cut out those foods. Score.

You keep going and the following week is also a success. You’re even enjoying the new obsession of carefully selecting and preparing your food, eating far more consciously crafted lunches than your colleagues. You can’t help but feel a sense of pride when your friend comments that you’ve been looking thinner and asks for your secret. A few more pounds fly off and your confidence is soaring.

As time passes, you’re starting to wonder whether you really need to be so rigid with your eating. Perhaps you can be “bad” from time to time given that you’re usually so “good.” You loosen your rules. No carbs at lunch, but dinner is okay. Eat all I want before 7 p.m., but nothing after that. Dessert once a week should be fine.

Sam Thomas, iStock
Source: Sam Thomas, iStock

This works for a bit, but soon situations arise where even your relaxed rules feel too strict. So, you cave and break your seemingly solid plan. Much to your dismay, your clothes start to feel a bit tighter and the number on the scale starts to creep upward. You start to question how you could have let this happen. Guilt ensues and you vow to make reforms next week.

Throughout all of this, something else starts to happen: It feels as though food has complete control over your life. You’re thinking about it all the time, constantly evaluating your dietary choices and the impact these are having on your weight. You’re experiencing strong cravings for foods that you know you’ll feel guilty eating. Is this just more evidence that you need to keep dieting? Is there something wrong with you?

No; this is actually a natural consequence of dietary restraint. When we are engaged in dietary restraint, we are trying to watch what we eat and have a mental sense of the types and quantities of food we would like to be avoiding, whether or not we’re being successful. There’s a lot of research showing that restrained eaters are much more likely to obsess about food and to develop overeating habits than intuitive eaters, who eat what they feel like according to how hungry and full they feel.

A lot of research shows the power that food has over restrained eaters, especially when they break their dietary rules. In one classic study, the researchers asked restrained and non-restrained eaters to drink 0, 1, or 2 milkshakes. Then, all participants had the chance to "taste test" as much ice cream as they wanted. What the researchers found was that the more milkshakes the non-restrained eaters consumed, the less ice cream they tasted. The restrained eaters, however, showed the opposite pattern: the more milkshakes they drank, the more ice cream they ate. Why?

The method is in the milkshake. The more milkshake restrained eaters consume, the more likely they are to feel that they’ve broken their diet. So, after a milkshake, the logic is, “Might as well go crazy on the ice cream since I’ve already ruined my diet.” This phenomenon is known as the disinhibition, or “what the hell,” effect and highlights that mental forces direct their eating. Non-restrained eaters don’t have rigid dietary rules to begin with: a milkshake is always fair game and ice cream is nothing special. Physical cues of hunger and fullness direct their eating, so they will naturally eat more ice cream after one milkshake and less after two milkshakes.

This knowledge might inspire you to try and let go of restrained eating and work toward eating more intuitively – based on physical hunger and cravings rather than mental rules. But this might feel scary, especially in today’s diet culture. The initial phases of reducing dietary restraint require deliberate practice and planning. But with time, intuitive eating comes to feel natural and freeing.

It can also help to know that although intuitive eaters don’t have rigid rules around food, they tend to eat nutritiously and have lower body-mass indices than restrained eaters, in part because dieting often causes weight gain over time. However, beware of approaching intuitive eating with the goal of weight control as this will keep you in a restrained mindset without realizing it. 

If you want to experiment with switching from restrained to intuitive eating, here are some initial steps you can take.

1. If you currently try to limit your intake of certain foods or food groups, start planning to allow yourself to eat those foods. If you limit carbs, pack a sandwich for lunch instead of salad. If you do this, it will be important that you don’t remove carbs from other parts of your day as doing so will just refuel the restrained mindset.

2. Identify your other rules around eating and make a deliberate plan to break them. For example, if you have a rule not to eat during a certain time of day, start having a planned snack every day in that time frame but be sure you don’t “pull back” at other times of day to compensate. Otherwise, you will still be a victim to the restrained mindset.

3. Set out to eat three meals and three snacks a day. This helps to convince your mind that you’re not actually trying to restrict eating, and the sense of restraint can fade away.

4. Notice what happens as you start to deliberately eat in this more flexible way. Does it feel more freeing and more enjoyable? Are your urges to “indulge” and overeat as high as they were before? We suspect the answer will be no. After all, it’s hard to desire something you already have.

5. Thank yourself for letting your body eat what it wants to eat, and weigh what it wants to weight. Ultimately, as we let go of restraint, we are letting go of the desire to control our weight and allowing it to settle where it wants to settle. This is ultimate freedom.


Bacon, L., Stern, J.S., Van Loan, M.D., Keim, N.L. (2005).  Size acceptance and intuitive eating improve health for obese, female chronic dieters. Journal of the American Dietetic Association, 105(6), 929-936.

Denny, K. N., Loth, K., Eisenberg, M. E., & Neumark-Sztainer, D. (2013). Intuitive eating in young adults. Who is doing it, and how is it related to disordered eating behaviors? Appetite, 60, 13–19.

Fairburn, C. G. (1995). Overcoming binge eating. Guilford Press.

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Tylka, T. L. (2006). Development and psychometric evaluation of a measure of intuitive eating. Journal of Counseling Psychology, 53(2), 226–240.

Urbszat, D., Herman, C. P., & Polivy, J. (2002). Eat, drink, and be merry, for tomorrow we diet: Effects of anticipated deprivation on food intake in restrained and unrestrained eaters. Journal of Abnormal Psychology, 111(2), 396-401. doi:10.1037/0021-843X.111.2.396