5 diet myths that are sabotaging your weight loss

why cant i lose weight
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Trying to lose weight? You could be doing more harm than good if you’re listening to these wrong but commonly held beliefs about dieting.

Why can't I lose weight?! It's a question many of us have asked. You've tried 2020's best diets, as well as classic regimes like the Cambridge diet. Yet you just can’t seem to shed your spare tyre, no matter how hard you try. The problem however, might not be with your willpower. It might be more to do with the advice you’re following. Turns out, that many diet facts we believe to be true, are actually fiction.

Research is revealing that there’s lots to learn about how we gain and lose weight and exercise.

Here are five myths you should know about – and how to beat them…

Why can't I lose weight: 5 common reasons

These common myths could be the reason you're not losing weight.

Myth 1: Exercise more

Why we believe it

Regular exercise burns calories and is essential for good health.

Why the myth isn’t true

Exercise will help you maintain a healthy weight, but increasing your exercise while you start a weightloss programme can work against you, says diabetes expert Prof Roy Taylor.

‘Increasing your exercise levels will increase your appetite, making it harder to stick to your weightloss plan.’ Also, research shows that we are likely to over estimate the calories our exercise has burned and then “treat” ourselves with a high-calorie reward, which often undoes all our hard work.

What you should do instead

When you start your weightloss programme don’t up your exercise levels at the same time. ‘Keep them the same until you have lost the weight your need to,’ says Prof Taylor, author of Life Without Diabetes (£7, Short Books). Then gradually increase your activity levels and be aware of how many calories you are actually burning and don’t be tempted to reach for a “reward” Kitkat.

Myth 2: Carbs make you fat

Why we believe it

Refined carbohydrates are broken down very quickly into simple sugars and if we eat too many of them and don’t burn the excess energy it will be converted into fat in our bodies.

Why the myth isn’t true

Too many carbs can make you fat. But too much of any food causes weight gain. Carbohydrates are a useful and affordable source of energy and although they’re not an essential nutrient, such as fat or protein, it’s best not to cut them out of your diet completely.

What you should do instead

Watch your portion sizes and choose your carbs carefully. ‘There’s a massive difference getting your carbs from a white sliced loaf versus wholegrain rice or whole rolled porridge oats,’ says Harley Street nutritionist Kim Pearson. ‘Avoid white flour products. They’re refined, which means they’ve had their vital nutrients (minerals and fibre) stripped away and they’re broken down very quickly into simple sugars in your bloodstream contributing to energy slumps and diabetes.’

Myth 3: Eat little and often

Why we believe it

Grazing stops us feeling hungry and constantly stokes our metabolic processes and burns calories.

Why the myth isn’t true

The act of eating doesn’t burn more calories than you consume from the food you are actually eating. And most of the foods we snack on are highly processed and high in calories, and it can be trickier to keep track of exactly how much we are consuming. Constant grazing is one of the main reasons health experts think we have an obesity problem - our obsession with snacking has spawned a multi-million pound industry with encourages us to eat even more between meals.

What you should do instead

If you want to know how to eat less, stick to three balanced meals a day without snacks to help keep your weight under control and give your digestion a rest, says Dr Melanie Wynne Jones. ‘Fasting (no-snacking and/or prolonging the time between your evening meal and breakfast) can help blood and insulin levels and other metabolic processes.’

Myth 4: A cardiovascular workout is best

Why we believe it

Because cardio (aerobic) exercises, such as running, cycling and swimming, burns more calories.

Why the myth isn’t true

While cardio exercise does burn fat, it also reduces your muscle mass, says Kay Miyake from PureGym (puregym.com). And muscle mass is important for weightloss too. ‘Muscle mass can influence your basal metabolic rate, which influences how many calories you naturally burn at rest,’ says Kay. ‘By including weight training into your routine alongside cardiovascular activities you can help to offset the rate of muscle mass loss.’

What you should do instead

Include some weight training as well as cardio to help maintain weightloss ‘Weight training has been shown to increase the calories burnt after an initial exercise period,’ says Kay. ‘Plus, weight training also provides lots of other health benefits that you may not get from cardiovascular exercise, such as improving strength and bone density.

Myth 5: Eating in the evening makes you fat

Why we believe it

We’ve all heard that we somehow burn calories more slowly at night compared with during the day, and that if we eat late in the evening, the calories deposit themselves more readily into fat cells.

Why the myth isn’t true

‘It’s not when – but what – you eat,’ says nutrition scientist Dr Susan Jebb. Your metabolism is fairly consistent over a 24-hour period. ‘If you eat more calories than you expend through activity, you’ll put on weight.’ Eating earlier, however, does allow you to do some calorie-burning activity, such as a post-dinner walk. And the evening, when we’re often less busy, can be when we reach for unhealthy snacks.

What you should do instead

Look at what you eat in a whole 24-hour period, not a few hours in isolation. If your lifestyle means you can’t eat an early evening meal, that’s not a problem, so long as your total overall consumption is sensible.

Hopefully you won't have to ask why can't I lose weight for much longer...

Tanya Pearey has been a writer and editor in the health, fitness and lifestyle field for the past 25 years. She writes regularly for women’s lifestyle titles including woman&home. She has also written for newspapers including The Daily Mail and Daily Express, and women’s magazines in Australia. 


Tanya is an avid runner and is lover of Parkruns and half marathons. She completed the London Marathon in under four hours – but that was 20 years ago! She’s a keen tennis player and walker, having climbed Kilimanjaro and the UK’s three highest peaks - Snowdon, Ben Nevis and Scafell Pike.