Why diets don’t work

Two friends cooking together in a kitchen

It’s not surprising that we are seduced into dieting. We live in a society that praises thinness in women and muscularity in men, and these traits are portrayed as something to be desired – a sign of confidence, health, and achievement. Therefore, if we do not fit into this mould, we can be made to feel unhealthy, lazy and “less than”.

The diet industry capitalises on this societal standard by making us believe that we need to shrink our bodies to feel worthy. The worse you feel about yourself, the more likely you are to spend your money on diet after diet.

The reason it is such a profitable £2 billion industry is that diets don’t work. When one diet inevitably fails, there are hundreds more into which you can sink your cash. So, what are other costs of dieting?

Studies suggest that if we follow a diet, any ensuing weight-loss is often short-term and comes at a cost. What these studies don’t show you is what happens to the participants’ weights in six months, one year or five years’ time. Studies that have looked at longer-term outcomes of dieting find the same thing you may have experienced if you’ve been on a diet – weight is regained back to pre-diet levels, if not more.

And not just that, but metabolism slows down (really not great for long term weight maintenance) and body satisfaction decreases. The yo-yoing in weight that happens after going on diet after diet can be more damaging to our physical health than maintaining a higher weight i.e. not dieting in the first place. Not to mention, there are detrimental psychological and emotional effects of being on a diet and feeling you are “failing”. We hope you can see now, however, that this feeling of failure results from unrealistic expectations placed by the dieting industry. This is not an individual failure!

Image of a woman in a yellow top eating with friends

When we diet or restrict our food intake we can cause some immediate detrimental effects on our body. About two-thirds of our daily energy requirements are for the essential functions in our body, just to keep us alive. These functions include keeping our heart pumping, lungs inflating, kidneys filtering, blood circulating and brain neurons firing – and that’s if we were fast asleep in bed, not moving a muscle.

All the while, our body is doing some really hard work. Add to that the energy it takes to digest and absorb our food, for our immune system to keep us from getting sick or helping us recover from illness, for our body to constantly grow and repair itself, to produce testosterone or oestrogen/progesterone (and having a regular period), as well as our normal daily activity.

If we are deprived because we have taboo foods, then we need to make peace with food and start giving ourselves permission to eat these foods again

So when we aren’t eating enough and/or we exercise so much so that we lack the available energy for our body to fuel these functions, something has got to give. The body starts to prioritise: what functions can it stop expending energy on that is not going to keep us alive? Common reactions to dieting therefore include:

  • tiredness and fatigue
  • reduction in sex drive
  • menstruation stops or becomes irregular in women
  • deterioration of quality of skin, hair and nails
  • feeling cold

All of these occur because our body is trying to conserve energy for vital functions. But what if we continue to restrict our food intake or force our body to expend more energy by exercising? Well, we start to break down our own body’s stores for energy. Yes, this can include our fat stores, but it also includes our muscles. We really don’t want to lose muscle, because muscle and our metabolism (the rate at which we convert food into energy) are closely related: losing muscle means our metabolism slows down. A slow metabolism often means rapid weight gain and difficulty maintaining a healthy weight in the long-term.

At this point, our body works even harder to conserve energy, so it will try to slow everything down. That means our:

  • heart rate slows down
  • blood pressure drops
  • digestive system slows down, which means you feel more bloated, constipated or have more abdominal discomfort than before
  • brain slows down, leading to difficulty concentrating, problem-solving and thinking in general
  • metabolism slows down

Doesn’t look good, does it?

Even if you’re not that bothered about the physical consequences of dieting, think about the way it affects your relationship with food. Ever been on a diet to lose weight and it works for a bit, but then you seem to “fall off the wagon” and eat anything (or everything) you find in the cupboard because you’re just too damn hungry? You blame it on being greedy or not having enough willpower, but it can be summed up in one word: deprivation.

Deprivation can be physical or psychological. When you consistently do not eat enough, your body will crave energy because you are forcing it into a negative energy balance, which it doesn’t like. We need food for fuel, and we need it to survive. When running low, our body will drive us to eat so that we have enough energy for our vital functions and to keep us healthy! So when we are depriving it of energy, we get hungry and crave foods, which can lead to out of control eating or eating way past comfortably full. This leads to feelings of guilt and regret and so the cycle continues.

Deprivation can also involve restricting certain types of food. Have you ever said to yourself, “I’m never going to eat chocolate or crisps again”, and then, although you may resist at first, the craving gets so intense that you end up eating a whole family-size bar/pack? Yep, that’s deprivation right there. You may be eating enough throughout the day, but you are not allowing yourself to eat the foods you want. This gives them a special and powerful status in your mind, which they don’t need to have.

Image of two male friends drinking together in a restaurant

If we are deprived because we have taboo foods, then we need to make peace with food and start giving ourselves permission to eat these foods again, whenever we want, and as part of a healthy balanced lifestyle.

Deprivation can also trigger “last supper” eating. Say, for example, you have put chocolate on your “forbidden foods” list. On the occasions you eat chocolate, you then push the “I give up” button and think, “I’ve messed up now and so I may as well eat the whole pack…” You may even think that you need to get rid of the food from the house by eating it all so that you can start the diet afresh tomorrow. All this probably would not have happened if chocolate wasn’t banned in the first place.

We also deprive ourselves by depriving our body of its natural weight and shape. Just like we are born with a predetermined height, we are also born with a predetermined weight range. This is called our set point range. Although like our height, our weight can be influenced by the environment, e.g. if we have suffered neglect and poor nutrition, it is mostly influenced by our genetics. In other words, our set point range is not easy to nor intended to shift.

If we diet and lose weight, our body tries its hardest to regulate our weight and get it back to our set point range. It does this by sending out hunger signals, increasing the number of thoughts and obsessions around food, and slowing down our metabolism. If we ignore these signals, our body just works even harder to do this, so it can result in out-of-control eating. The myths that we can choose to lose weight below our natural range and that we can diet healthily, are so damaging. We cannot change our genetics.

To have a better relationship with food and our body, we need to work on acceptance of the body we naturally have, stop depriving ourselves and kindly give our body the nutrition it needs to function

Diets can keep us focused on body shape and weight as a means of feeling happy, successful, or lovable. The consuming nature of diets shifts our attention to food and bodies and takes away from our ability to think and give attention and energy to the other things that matter to us in life – our values and goals.

When diets begin to take priority, sometimes our friendships, family, hobbies and career can begin to fall to the side. This tends to make people feel more unhappy, and more likely to seek ways to change or make themselves feel better, like another diet. It is important to ask yourself what your goal is. What are you hoping the diet and weight loss will ‘fix’? Then ask yourself: might there be another way of reaching this goal that doesn’t have the negative side effects of a diet? Refocusing on happiness, pride and connection with others in life are actually more strongly linked to the health improvement you seek anyway.

For many, dieting is seen as the answer but really, it is the problem. Diets are largely ineffective in the long-term and lead to a variety of detrimental physical and psychological consequences. To have a better relationship with food and our body, we need to work on acceptance of the body we naturally have, stop depriving ourselves and kindly give our body the nutrition it needs to function. Otherwise, we will continue to damage our physical and psychological health and feel inadequate and unhappy in the process.


Heal Your Relationship with Food: Effective Strategies to Help You Think Differently and Overcome Problems with Eating, Emotions and Body Image is published by Trigger Publishing (RRP £12.99) available online and from all good bookstores.

By working with a qualified nutrition professional, you can learn more about what makes a healthy lifestyle and understand what your body needs.

All of us are different and what works for one person, might not work for another. Working with a nutrition professional ensures you are making healthy changes safely. To find a professional near you or online, simply browse profiles and when you find a person you resonate with, send them an email.

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Maureen Moerbeck

Written by Maureen Moerbeck

Maureen Moerbeck is a registered dietitian and specialist eating disorders dietitian for the NHS.

Written by Maureen Moerbeck

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