BLOG BY Kimberley Neve ANutr

What Are The Side Effects of Dieting?

A survey last year found that adults will try 126 different diets during their lifetime, with an average of 2-3 a year.[1] The top five diets were the 5:2 diet (intermittent fasting), Atkins and keto diets (very low carbohydrate), a cabbage soup diet and juice cleanses. You will likely have tried one of these fad diets yourself. They are called ‘fad’ diets because they promise fast weight loss with a significant reduction in energy intake that is not sustainable long-term.

The cycle of dieting, losing weight, stopping the diet and then gaining weight is called the ‘diet cycle’. It may also be referred to as crash, or yo-yo, dieting. Although weight loss can lead to health benefits (depending on the person’s medical history and health status), continuous weight loss and regain may actually be harmful to health long-term, making fad diets dangerous as well as demoralising.

What counts as a fad diet?

Diets are a way of eating. They can simply be a way to describe what or how people eat, but more commonly, diets are known as a way to lose weight. Fad diets contain restrictive rules around eating, which is partly why they are so hard to follow for a long period of time. If you are unsure whether something is a fad diet, consider the following questions:Is there a set meal plan that you have to follow?

• Is a food group restricted, for instance carbohydrates?

• Are there 'cheat' days, or 'cheat' foods?

• Are there rules to break?

• Are you counting calories or points?

• Can you 'fail'?

If you said yes to any of these, the diet is likely to be unsustainable for a long period of time. For the large majority of us, that means that we stop the diet at some point, and often put any weight we lost back on - in many cases, research has shown that we put more on.[2] It is estimated that over 95% of people who diet regain the weight after three years.[3]

Why are diets so hard?

After the initial weight loss, our body responds by conserving energy and increasing hunger so that you are more inclined to eat. Evolutionarily-speaking, we have not caught up yet to our food environment where food is nearly always available. When you suddenly eat less, your body adapts, sending messages via hormones and neurotransmitters to your brain to eat more so that you can survive.

A further adaptation is to slow the body’s energy usage down, which is why you might feel tired on a diet. After a while, your body gets used to you feeding it less and require fewer calories to run - this is why after a few diets, you might find that you have to reduce calories even further to get the same effect as before.

More often than not, when motivation wanes because weight loss plateaus and the rules of the diet are too difficult to sustain, you stop the diet. This is nearly always seen as a ‘failure’ or a lack of willpower; yet, if diets were intended to work, you would only ever do one! Starting diets again and again is what makes the diet industry an estimated £2 billion a year in the UK alone.[4] What is less clear is how going up and down in weight, or ‘weight cycling’, can affect us both physically and psychologically. 

Are there side effects to dieting?

Research into how repeated episodes of weight cycling affects us is still limited, and it is difficult to draw comparisons with differing definitions of what counts as weight cycling, i.e., how much weight or body fat someone has to lose and regain for it to be counted as weight cycling.

That said, many studies have shown that weight cycling may be associated with negative health outcomes, including: a higher BMI, higher body fat percentage, larger waist circumference, greater fat mass distribution to the upper body, lower resting metabolic rate, increased risk of hypertension and decreased glucose tolerance.[5] Yo-yo dieting has also been linked to binge eating more[6] and more frequent visits to the doctor.[7]

Psychologically, weight cycling is associated with lower self-esteem[8], a higher risk of depression[9] and increases in the severity of Binge Eating Disorder (BED).[10] This makes sense if you have ever dieted before and know that feeling of ‘failure’ when you are not able to keep it up. The restrictive nature of fad diets can also trigger BED, which in itself is associated with depression and anxiety, as well as weight cycling.[11] For some people, the different food rules from fad diets can lead to misunderstandings about what constitutes a healthy diet and very restrictive eating practices focusing only on ‘clean’ or healthy foods, known as orthorexia. This can also lead to feelings of anxiety, low mood and depression.[12]

Weight cycling also affects your future attempts at weight loss: when trying to lose weight as part of an intervention, people who had yo-yo dieted before lost less fat and more lean mass than those who had not previously dieted.[13] Furthermore, a separate study showed that when weight is regained following weight loss, people who had dieted previously put on a higher proportion of fat.[14]

Although there is increasing evidence that weight cycling has serious side effects, not all studies agree and it is still unclear whether it is safer or more dangerous to lose and regain weight or remain overweight and not attempt weight loss.[15] The takeaway: forget the fad diets and focus on overall health and lifestyle.

Should you go on a diet?

If you are reading this and thinking: “So, is it impossible to lose weight and keep it off?” The answer is no, it is not impossible! However, restrictive diets can impact negatively upon your mental health[16] and fast weight loss is extremely unlikely to work long-term. If weight loss is important to you, here are some tips that will help you long-term.

3 Tips for Long-Term and Sustainable Weight Loss

1. Be in it for the long haul. It really does have to be a lifestyle change so that you eat that way forever, which just means making small changes over a long period of time. Aim for consistency rather than perfection, because a) there is no such thing as a perfect diet and b) it will give you better results over time.

2. Enjoy your food! This is what makes a diet a lifestyle and also helps you to feel more satisfied after you eat. Make sure your meals and snacks are ones that you genuinely like the taste of and look forward to eating.

3. Focus on other measures of health instead of weight. Consider things like overall body composition, sleeping more, better digestive function, healthier hair and skin, better mood and general happiness.

Kimberley Neve is a Registered Associate Nutritionist specialising in weight management. She owns Neve Nutrition and Wellbeing, offering personalised nutrition consultations to help clients stop dieting and make positive changes that last and become a new lifestyle. She also works in food environment research, advising the Department of Health and Social Care on healthy eating policy in England.


[1] https://www.studyfinds.org/food-fads-the-average-adult-will-try-126-different-diets-during-their-life/

[2] https://pubmed.ncbi.nlm.nih.gov/22475574/

[3] https://pubmed.ncbi.nlm.nih.gov/23859104/

[4] https://www.bhf.org.uk/informationsupport/heart-matters-magazine/news/food-trends-2016/do-not-follow-food-trends

[5] https://onlinelibrary.wiley.com/doi/full/10.1111/obr.12232

[6] https://pubmed.ncbi.nlm.nih.gov/15263922/

[7] https://pubmed.ncbi.nlm.nih.gov/15800292/

[8] https://pubmed.ncbi.nlm.nih.gov/19328269/

[9] https://pubmed.ncbi.nlm.nih.gov/29277416/

[10] https://onlinelibrary.wiley.com/doi/abs/10.1002/j.1550-8528.1997.tb00674.x

[11] https://pubmed.ncbi.nlm.nih.gov/16815322/

[12] https://www.beateatingdisorders.org.uk/types/orthorexia

[13] https://pubmed.ncbi.nlm.nih.gov/20052347/

[14] https://pubmed.ncbi.nlm.nih.gov/21795437/

[15] https://onlinelibrary.wiley.com/doi/full/10.1111/obr.12232

[16] https://pubmed.ncbi.nlm.nih.gov/8655907/

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