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Why diets don’t work

diets don't work

Please don’t diet again

Dieting is not a topic that I write or even talk about very often, and that’s because DIETS DON’T WORK.

But why then is the diet industry making so much money? Because diets don’t work! You try one diet, immediately lose a few kgs but when life goes back to normal, you put those kilos back on. The next new diet trend comes along, you sign-up to another program, lose weight, gain weight, next program…and on…and on…$$$

Diets come in all shapes and sizes – shakes, pills, ready-made meals, cutting out dairy/gluten/grains, detoxing, keto – best described in a word RESTRICTION. In the short term, any diet will “work” – you will lose weight as measured on the scales.

But what about long-term? What’s happened 12-months after the 6-week shred or 12-week online program has finished, what then?

The vast majority of people who go on a “diet” regain any weight lost and quite often plus some, once they return to normal eating behaviours and habits.

So why don’t diets work? Simple really – our bodies were designed and have evolved to survive in times of feast AND famine (diet). I am sure you’ve heard all of the following before, but here’s a snapshot of what happens when you reduce or restrict calories, in other words, go on a diet:


Despite all the willpower and mental energy you can muster, your physical body just doesn’t understand dieting. Although we’d like to think this is what the brain is saying to the body…

“I’ve noticed that Jacqui’s cut back on her food recently. She must be back on that summer bikini-body shred diet. Hey, Metabolism, even though fuel is a little light on at the moment, let’s keep things at full throttle so Jac can lose that extra 5kg she’s gained.”

Unfortunately, (or fortunately) our physical bodies are only concerned with one thing – SURVIVAL. The following thought is a little more like what is registered…

“Hmmm, fuel appear to be in short supply at the moment. Hey Metabolism, turn down the flame to a gentle simmer, we need to conserve energy. I’ll send out the hunger hormones to try and bump up supply again”.

So, when food or energy supply is reduced to a level lower than what we optimally need, our body’s natural survival mechanism is to slow down metabolism to help the body function on fewer calories leaving more to store as fat.


In addition to your metabolism slowing down in response to calorie restriction, the hormones that control appetite and feeling full are messed up too. Despite what you might think, these hormones actually do the opposite when we are underfed.

The hormone that tells the brain we have eaten enough, Leptin, has been found to DECREASE with calorie restriction, meaning we need to eat more to feel full.

Ghrelin is the hormone released to stimulate your appetite and this has been found to INCREASE in times of calorie restriction or under eating.

Combine the two and we have the perfect storm of both feeling hungry and not feeling satisfied or full with what we have eaten – which together lead to wanting to eat more, not less!


In addition to a slower metabolism and messed up hormones, a diet also plays havoc with our thinking. Food becomes more tempting the longer you deprive yourself of it.

Ever noticed that when you have told yourself you “can’t have cake” all you can think about is cake? We become obsessed with thinking about food, how long until the next meal, you notice every ad on TV about food, smell every bakery you walk past and even hear other peoples conversations about FOOD!

The reward response to food becomes stronger when on a diet too. Each time we eat, we get a little hit of dopamine (the hormone that helps control the brain’s reward and pleasure centres). Food becomes even more rewarding – that piece of cake that you tried not to eat for so long tastes even better when you do eat it.

As you can see, we are perfectly set up to fail a calorie restrictive diet. Our body is wired – metabolically, hormonally, neurologically – to stay alive and survive famine. Dieting is like fighting the unwinnable fight.

So what’s the message in all of this?

That by using weight-loss as a goal you are setting yourself up for failure. I’m not suggesting you throw in the towel and binge on junk food. But if you were to move the focus from weight loss to health improvement, the goal is quite a bit easier to achieve and weight loss may be a bonus side effect.

To keep things super simple, the basics of healthy living are:

  1. Move daily – less sitting, more standing, more moving
  2. Eat 5 or more serves of fresh vegetables & fruit a day – add in lots of colour & variety
  3. Don’t smoke
  4. Drink alcohol in moderation

Not that difficult really! The more boxes you tick, the longer you can expect to live.

If weight loss is your goal, I hope you can now see that you will constantly be on a roller-coaster – physically, emotionally and mentally. Why not set yourself up to win and focus on improving your overall health rather than the number on the scales.

“Your body is not your masterpiece – your life is”, www.momastery.com


“Secrets from the lab: The science of weight loss, the myth of willpower and why you should never diet again”, Professor Traci Mann

Precision Nutrition “Leptin, Ghrelin and weight loss” www.precisionnutrition.com

Eric M. Matheson, Dana E. King, and Charles J. Everett
Healthy Lifestyle Habits and Mortality in Overweight and Obese Individuals
J Am Board Fam Med January-February 2012 25:9-15