Why most diets don't keep the weight off

Woman tracking diet on phone
Crash diets have drawn criticism in recent years because they only work in the short-term. (Getty Images)

At any give time, around two-thirds of British adults are on a diet and actively trying to lose weight.

So why are so many disappointed when they fail to see the results of their hard work beyond the first few weeks?

One study published in The British Medical Journal looked at the effect of using diets for weight loss among 21,942 adults who were clinically overweight or obese, and found that after twelve months, the effects on weight reduction had largely disappeared.

Read more: The NHS' 12-week weight loss plan explained - Yahoo Life UK, 3-min read

An expert from the British Dietetic Association revealed that the reason most diets fail to help people lose weight in the long run is because they rely on immediate results that could be unhealthy.

Registered dietician Monika Siemicka spoke to Yahoo UK about the need to change the way we look at dieting.

Which diet is best for weight loss?

Woman holding a tape measure
The promise of weight loss is one of the main reasons why people go on diets. (Getty images)

Any diet which promises to help you lose large amounts of weight quickly is bad for your body long-term, according to Siemicka.

"We know that when someone loses a large amount of weight very quickly, they almost always regain it," she said. "This is because a crash diet messes around with your metabolism.

"Your metabolism just means how quickly you burn calories. If you suddenly start cutting out lots of calories, your metabolism is going to slow down. And when your metabolism slows down, your body doesn't burn as many calories."

The impact on your metabolism is an important reason why restrictive diets are not recommended by dieticians.

A restrictive diet is one that involves cutting out an entire food group. The keto diet is the most popular example, which involves mostly eliminating carbohydrates and replacing them with foods high in fat and protein.

Is the keto diet safe?

"We would never want anyone to cut out a specific food group as a whole, unless it's medically indicated, like a gluten allergy for example," Siemicka explained.

"Carbohydrates are often vilified in the media. But actually, they've got loads of goodness in them. If they're mainly whole grains, you've got loads of fibre in there. You've also got your B vitamins and they're really good for your gut."

Read more: A low-carb diet can increase your risk of mortality by up to 38% each year - Yahoo Life UK, 3-min read

"[If you cut out carbs], over the first few weeks, you might find that you lose weight but you actually lose quite a bit of water as well. The issue is what then happens in the long run - that weight loss will plateau and you might start feeling really hungry and then regain the weight."

Most dieticians recommend reducing the amount of carbs in your meal, rather than cutting them out and replacing them with fatty food.

Siemicka said: "You could sit down and look and how much of your plate is rice and think, ‘okay, I still want to have rice on my plate but I only want it to be a quarter of the plate and I want to fill the rest with protein and vegetables.

"That could then become a habit which you could do for the rest of your life and it’s much more sustainable than just cutting out carbs."

What effect does dieting have on mental health?

One of the common mental health impacts of going on a diet is feeling disappointed when you're unable to keep it up. This can lead to frustration and feelings of worthlessness.

Siemicka explained that this then discourages people from making healthy lifestyle changes, because they can't see the results that they're looking for straight away and don't think they will last.

frustrated woman
Being unable to follow a diet can lead to negative self thoughts. (Getty Images)

"There are many different ways that people can monitor their progress," she said.

"Maybe just not even using the scales as an outcome, but thinking about two or three other things that you can focus on to know if a diet is a right for you: Are your energy levels better? How are your stress levels? Do you feel better in yourself?

"A lot of the choices we make about food come down to our psychological state."

Read more: Woman loses 15st after ditching tinned fruit habit: 'I’d wake up choking because my neck was so big' - Yahoo Life UK, 2-min read

Siemicka added: "I would say somebody's body shape or body size tells you nothing about how healthy they are because you can't see what's going on inside.

"We should move away from looking at people and making judgments."

The British Dietetic Association is a professional body representing practitioners, researchers, educators, support workers and students who work in dietetics. You should always consult your GP before making drastic changes to your diet.

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