Why don’t diets work? Want a one-sentence answer?

As the BMI (body mass index) people have goes up, the prevalence of dieting goes up!

That correlation should be proof enough. If dieting worked, it would be the lean people who had dieted.

I certainly understand why you might want to diet. You want a quick fix. You want results now, not over the long haul. You also want something specific to follow so you don’t have to think about your choices. You have enough to learn, enough decisions to make every day. The advertising is certainly alluring, as are the testimonials you get from friends – short-term. But do you know ANYONE who’s followed a diet and kept the weight off? Or even anyone who’s dieted and not gained even more weight back than they originally had?

National Institutes of Health studies show that 98% of people who diet and lose weight gain it back within 5 years, and 90% gain back more than they lost.

Unfortunately, since diets do work for the short-term, people keep trying them thinking they’ll work again.

How do diets work?

  • They work by cutting calories. If you are eating less than you are burning, you will lose weight.
  • They work by making it difficult to eat. They limit what foods you can eat, what time you can eat, what foods you can eat together, or some other method of restricting your usual eating patterns.
  • They work because when you know you’re on a diet you’re conscious about what you’re eating and deprive yourself of the things you might otherwise eat.

Yes, diets work short-term, but they work against you long-term.

Why don’t diets work long-term?

  • It’s just too hard to stick to deprivation diets in our world. There are temptations at restaurants, the grocery store, and anytime you’re a guest at someone else’s house. There are always celebrations or other occasions when you “deserve” to cheat, and then it just becomes exhausting to always be on guard and have to think too much about what you should eat.
  • Diets are so depraving, they can cause you to rebound into overeating.
  • Diets don’t teach you to eat healthy for life. They teach you to stick to depriving yourself for a limited amount of time. A temporary fix will give you temporary results. Go back to your old ways of eating, and you go back to your old weight.
  • If you diet to lose weight, your metabolism drops at a rate of 8 calories per day per pound of weight lost. That’s 320 less calories you’re burning per day if you lost 40 pounds. So, if you go back to just eating like you did before to maintain your weight, you’ll be eating 320 calories per day more, and gaining 32 pounds by the end of the next year!
  • You lose 5-10 pounds of calorie-burning muscle mass each decade starting at about age 25. That means you’re burning 500 less calories a day by the time you’re 65 – unless you do something to avert it. If you diet without strength training to build or at least preserve muscle, you’ll lose even more muscle each time you diet, and your metabolism will drop to even lower than it was before.

What works:

  • Eat for health. If you focus on eating foods high in vitamins and minerals, your body will get the nutrients it needs and be less likely to crave more food.
  • Make sure you’re drinking enough water or other no- or low-calorie drinks. Often your body gets hunger signals mixed up with signals for thirst.
  • Make sure you’re getting enough sleep. It’s been shown people eat more for energy when they’re sleep-deprived.
  • Write down what you eat. Yes, it’s a pain to keep a diary, but the simple act of writing down your food has been one of the ways proven to change your regular eating habits. It’s amazing what choices you make when you’re conscious of them, and accountable for writing them down – even if it’s only for your own eyes.
  • Be aware of portions. Portions of each of 3 or 4 food groups at a meal should be no bigger than the size of the palm of your hand. Serve what you should eat and don’t go back for seconds. Yes, that means buffets are torture! It also means if you are served more than you should eat when going out to a restaurant, it’s a good idea to ask for your doggie bag before you even start eating. Put aside what you’ll bring home for your next snack or meal.
  • Eat foods high in water and fiber content to make you feel more full (fruits, vegetables, whole grains).
  • Eat your calories, don’t drink them. Limit frapuccinos, juices, and other high-calorie beverages.
  • Pay attention to whether you really feel full or if you’re eating unconsciously or for emotional reasons. Learning to stop when you’re not hungry anymore instead of when you’re full, will prevent you from eating too much in one sitting.
  • Eat small frequent meals. Food has a thermogenic effect on your body. Each time you eat, your metabolism speeds up. Skipping meals causes your metabolism to slow down and your body to go into preservation (fat storing) mode.
  • Be mentally and emotionally ready. Instead of attempting to change your habits, make sure you’re really ready to make the commitment to change.
  • Be realistic. Moderate changes will not produce results overnight. Remember how long it took you to put the weight on, and expect it to take that long for it to come off.
  • Be flexible. Allowing yourself a treat every once in a while is different from eating treats all the time. And denying yourself treats is no way to live either.
  • Set goals that are specific, measurable and for a certain timeline. Writing them down will reinforce them too.
  • Make small changes. They’re easier to keep. Go from cream to whole milk, whole milk, to lowfat milk, lowfat milk to nonfat milk, etc. If you get used to the changes as you go, they’ll become the new norm instead of an extreme change that’s no fun to sustain
  • Be prepared for obstacles and develop a plan for how to overcome them. Look at daily eating, snacks, meals out, vacations, etc.
  • Make sure how you choose to eat is something you can live with for the rest of your life. If you don’t think you can, you won’t. Only lasting changes will produce lasting results.

To Assist With Your Healthy Eating for Weight Loss:

  • Incorporate strength training to build muscle and boost the amount of calories you’re burning all day long.
  • Change the exercises you’re doing to stimulate your body to change again.
  • Turn up the intensity of your exercise.
  • Simply move more throughout the day. Take the stairs, park further away, take breaks from your desk, and get off the couch!

With all of the above, you’ll be successful in achieving your weight loss goal AND keeping the weight off!


Berardi, PhD, CSCS, John M., “Getting Lean by Revving Up Your Metabolism”, 2006.
Adair, MS, RD, Dominique, “The Diet Scam: Deconstructing Fad Diets”, 2006.

Why Diets Don’t Work