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Six weight loss myths

Samantha Wild
Clinical Lead for Women's Health and Bupa GP
23 July 2024
Next review due July 2027

There are lots of myths about weight loss and it can be hard to know what to trust. Fad diets don’t work for everyone, but there are some simple strategies for success. Here, I’ll cover some common myths surrounding calorie deficits, carbohydrates, and more.

person checking weight on a scale at home

Myth 1: I have to eat much less to lose weight

You might think the best way to lose weight is to cut out as many calories as you can. Several fad diets take this approach, and these are often very restrictive.

In the short term you may be able to lose weight on these diets. But they’re not sustainable. Many people find such extreme, fad diets, don’t work in the long term.

This is not because you don’t have enough willpower.

It’s because your body tries to protect you when you eat a lot less. It thinks you might be entering a phase of starvation. So, your body will:

  • increase your appetite
  • reduce your energy expenditure

This means you burn less calories at rest and during movement. After a short period of weight loss, you can then plateau (fail to lose more weight).

What’s a healthy calorie deficit?

Eating around 500 to 600 fewer calories each day is a more realistic calorie deficit. Reducing your calories by this much shouldn’t trigger your body to think it’s being starved.

So, your appetite won’t increase too much. With a calorie deficit of around 500 calories per day, you should lose around one to two pounds per week. Over time this can help you to meet your weight loss goals.

Myth 2: I should cut out all carbohydrates

Weight loss approaches such as the ketogenic diet remove carbohydrates. For some people, this can work well in the short term. This is because when you cut out carbohydrates you usually reduce your calorie intake too.

But studies have shown that cutting out carbohydrates means people usually don’t get enough fibre. This can have a long-term effect on your gut health, and may also increase your risk of heart problems.

Instead of cutting out carbohydrates altogether, you could switch to complex carbs such as brown rice, brown bread, and wholemeal pasta. These foods:

  • release their energy slowly
  • are high in fibre
  • help to keep you full

Keeping carbohydrates to a quarter of your plate can also help you to reach your calorie deficit.

Myth 3: Exercise is as effective as diet for weight loss

Exercise is incredibly important for your physical and mental health.

Moving more can help you to use extra calories during the day. Strength training is also useful for weight loss because it increases your muscle mass. Having more muscle mass means you burn more calories, even at rest.

But exercise is not as effective for weight loss as watching what, and how much, you eat. This is because it’s easy to:

  • overestimate how many calories you burn during exercise
  • underestimate how many extra calories you eat after exercising

Myth 4: All calories are equal

A calorie from an apple has the same energy as a calorie from a biscuit.

But the way that these foods affect your weight, and your health, is very different. This is because when you eat ultra-processed foods such as biscuits or crisps, it’s easier to overeat. So, it can be harder to stick to a calorie deficit if you eat a lot of these foods.

Getting more of your calories from real foods such as apples, nuts, or fish can help. These foods are likely to keep you for longer because they contain fibre and protein.

Minimally processed foods such as vegetables and wholegrains also contain key vitamins and minerals that ultra-processed foods lack.

Myth 5: Stress and sleep don’t affect my weight

It’s not only what you eat that affects your weight.

Studies have shown that poor sleep can lead to overeating. People who sleep less are more likely to crave high-calorie foods and drinks the next day because these can provide more energy. Eating these foods frequently can cause weight gain over time.

Studies have also shown that poor sleep may affect your blood glucose level. This can increase how much energy is stored as fat in the body.

So, making sure you focus on getting enough quality sleep can help. Going to bed and getting up at the same time every day can help to regulate your body clock and support good sleep.

Chronic stress may contribute to weight gain too. One study showed that high cortisol (a stress hormone) levels may increase levels of visceral (belly) fat. So, try to find time to relax when you can.

Myth 5: I need to intermittently fast to lose weight

With intermittent fasting, you eat your food within a certain time window. For example, you might eat between the hours of 10am and 6pm.

For some people, intermittent fasting can support weight loss. This is because you:

  • cut out late-night snacking
  • eat less overall

But for others, intermittent fasting is hard. It can even lead to overeating because some people may compensate for the fasting by eating more at mealtimes. More studies are needed on the long-term risks of intermittent fasting.

So, if intermittent fasting doesn’t work for you, there’s no need to do it. Some people may find sticking to a 12-hour eating window is more realistic – such as eating within 7am to 7pm.


The Bupa weight management plan is designed for people with a BMI over 30 (or over 27 if you have a weight related condition). The plan is designed to empower you to achieve and maintain a healthy weight in a sustainable way.
Discover more about our medicated weight loss plan.

Samantha Wild
Dr Samantha Wild
Clinical Lead for Women's Health and Bupa GP

 

Co-author

Julia Ebbens, Health Content Editor at Bupa UK

    • Research says fad diets don’t work. So why are they so popular? American Heart Association. Heart.org, accessed July 2024
    • Faidon M. On adaptive thermogenesis: just another weight-loss tale? Am J Clin Nutr 2020;5. DOI:10.1093/ajcn/nqaa262
    • Your simple guide to healthy weight loss. British Heart Foundation. Esht.nhs.uk, accessed July 2024
    • Rew L, Harris MD, Goldie J. The ketogenic diet: its impact on human gut microbiota and potential consequent health outcomes: a systematic literature review. Gastroenterol Hepatol Bed Bench 2022;15(4):326-342. DOI: 10.22037/ghfbb.v15i4.2600
    • Keto diet is not healthy and may harm the heart. Harvard Health. Health.harvard.edu, accessed July 2024
    • Wholegrains. British Dietetic Association. Bda.uk.com, accessed July 2024
    • The plate method for weight management. Diabetes UK. diabetes.co.uk, accessed July 2024
    • Physical activity. World Health Organisation. Who.int, accessed July 2024
    • Robinson, E., Stensel, D. Does physical activity cause weight loss?. Int J Obes 2023; 47: 91–92. https://doi.org/10.1038/s41366-022-01247-4
    • Willbond SM, Laviolette MA, Duval K, Doucet E. Normal weight men and women overestimate exercise energy expenditure. J Sports Med Phys Fitness 2010;50(4):377-84
    • Physical activity guidelines for adults aged 19 to 64. UK Government. www.gov.uk, accessed July 2024
    • McPherron AC, Guo T, Bond ND, et al. Increasing muscle mass to improve metabolism. Adipocyte 2013;2(2):92-98. DOI: 10.4161/adip.22500
    • Ultra processed foods appear to cause overeating and weight gain. Harvard Health. Health.harvard.edu, published 1 August 2019
    • Glynn E, Fleming S, Edwards S, et al. Consuming a Protein and Fiber-Based Supplement Preload Promotes Weight Loss and Alters Metabolic Markers in Overweight Adults in a 12-Week, Randomized, Double-Blind, Placebo-Controlled Trial. J Nutry 2022; 152. DOI:10.1093/jn/nxac038
    • Ultra processed foods: how bad are they for your health? British Heart Foundation. Bhf.org.uk, accessed July 2024
    • Chan WS. Daily associations between objective sleep and consumption of highly palatable food in free-living conditions. Obes Sci Pract 2018; 17: 379-386. DOI: 10.1002/osp4.281
    • Sleep and weight loss. The Sleep Foundation. Sleepfoundation.org, accessed July 2024
    • 8 Health benefits of sleep. The Sleep Foundation. Sleepfoundation.org, accessed July 2024
    • Klingberg S, Mehlig K, Johansson I, et al. Occupational stress is associated with major long-term weight gain in a Swedish population-based cohort. Int Arch Occup Environ Health 2019; 92: 569–576. DOI:10.1007/s00420-018-1392-6
    • Welton S, Minty R, O'Driscoll T, et al. Intermittent fasting and weight loss: Systematic review. Can Fam Physician 2020 Feb;66(2):117-125
    • Ganson K, Cuccolo K, Hallward L et al. Intermittent fasting: describing engagement and associations with eating disorder behaviours and psychopathology among Canadian adolescents and young adults. Eat Behav 2022;47. DOI:10.1016/j.eatbeh.2022.101681
    • Nye K, Cherrin C, Meires J. Intermittent fasting: exploring approaches, benefits, and implications for health and weight management. JNP, 2024;20:3. DOI:10.1016/j.nurpra.2023.104893

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