COVID-19 Update

Our clubs are now open. Click here for more details about Les Mills at Level 2.

Why ‘diets’ don’t work (and what to do instead)

Many people believe that in order for a diet to be effective it just needs to help you lose weight. However, a diet didn’t work if you put the weight back on. You hear so many people talk about how they did a diet and it worked so well, however they slacked off, put the weight back on and really need to get back on track and get back on that ‘diet’. Those people are missing the point - they put the weight back on… therefore the diet did not work!

But more to the point of why a ‘diet’ doesn’t work. When people talk about diets they usually are talking about something that has an end point. They are on a diet to try get to a magical number, envisaging that when they reach this number they will be able to resume their way of eating as normal and all will be well. Wrong. The unfortunate truth of it is that when most people lose weight they will gain it back (and sometime more) within 1-5 years.

So why does this happen?

Going on a calorie-deprived diet relies solely on the theory of calories in vs. calories out. Now this works well, to an extent. The problem with chronic calorie deprivation and ‘quick fix’ weight loss is that it can alter your metabolism and the body’s ability to regulate fat storage/loss.

The Biggest Loser study is a great example of this. The study followed contestants from the wrap up of the show to 2015- 6 years on. They looked at body weight, fat percentage, resting metabolic rate and hormones (1).

After 6 years 13 of the 14 subjects had regained a significant amount of weight, whilst 4 of those are heavier now than what they were before they went on the show!

The average resting metabolic rate (RMR) of the participants was 2,607 kcal/day prior to the competition and dropped to 1996 kcal/day by the 30-week wrap up. Despite majority of the participants regaining a significant amount of weight, the mean RMR 6 years on was still only 1903 kcal/day! (1)

Put simply, the researchers found that their metabolisms were burning 500 fewer calories each day than expected given their new weight. No wonder they all had a tough time keeping the weight off!

Another interesting find was the significant reductions in the hormone leptin. Leptin is coined the ‘satiety hormone’ and is responsible for the long-term regulation of energy balance, supressing food intake and thereby inducing weight loss (2). Before the competition began the mean leptin, levels were around 41.14ng/mL. Post competition these levels had plummeted to an average of 2.56ng/mL (1). At the 6-year mark (and with the significant weight gain) leptin levels had only rebounded to around 60% of what they were.

This is thought to be due to thousands of years of survival tactics the body has developed to stop us from starving to death (3)- very handy back then but not so much now that we have an abundance of food all around us.

As depressing as this all sounds, there are strategies you can put into place that could help to minimise all these negative effects of weight loss.

1. Consult a qualified nutrition professional

Embarking on a severely calorie restricted diet you got from Woman’s weekly is probably not going to be your best bet. Consulting a nutrition specialist can save you a LOT of time, energy and money. They will take away the guesswork and allow you to embark on a plan that is going to work for life. Ensure this person is qualified (e.g. a registered nutritionist or dietician) so you get the best results!


Instead of embarking on strict calorie deprived plan; it makes sense to adopt a more sustainable ‘step wise’ approach that focuses on making one change towards better habits each week. This gives you a better chance at adapting to a healthier lifestyle without feeling overly restricted. So instead of trying to overhaul everything at once, pick one thing to solely work on that week, and only when you feel you have mastered that, move onto the next change the following week. These could be small changes such as reducing sugar in coffee or aiming to get 8 hours of sleep a night, but over time these sustainable small changes will make the world of difference and make you more likely to stick to it long term.

3. Limit stress

Stress affects our ability to train intensely, recover effectively and get enough sleep. It also directly affects fat-loss by promoting the ‘fight or flight’ response which includes providing more sugar to the body from internal stores. There is also an increase in cortisol with stress and that has been associated with weight gain (4). Assess areas in your life that bring you unnecessary stress and think of ways that you can minimise them. Meditation or stress apps can also work wonders.



  • 1. Fothergill, E., Guo, J., Howard, L., Kerns, J. C., Knuth, N. D., Brychta, R., Chen, K. Y., Skarulis, M. C., Walter, M., Walter, P. J. and Hall, K. D. (2016), Persistent metabolic adaptation 6 years after “The Biggest Loser” competition. Obesity, 24: 1612–1619. doi:10.1002/oby.21538
  • 2. Klok, M. D., Jakobsdottir, S. and Drent, M. L. (2007), The role of leptin and ghrelin in the regulation of food intake and body weight in humans: a review. Obesity Reviews, 8: 21–34. doi:10.1111/j.1467-789X.2006.00270.x
  • 3. Greenway FL. Physiological adaptations to weight loss and factors favouring weight regain. Int J Obes (Lond). 2015 Aug;39(8):1188-96. Review.
  • 4. Donoho, C. J., Weigensberg, M. J., Emken, B. A., Hsu, J.-W. and Spruijt-Metz, D. (2011), Stress and Abdominal Fat: Preliminary Evidence of Moderation by the Cortisol Awakening Response in Hispanic Peripubertal Girls. Obesity, 19: 946–952. doi:10.1038/oby.2010.287


Emily White - Nutritionist crop.jpg

  Article supplied by Emily White

 Emily White (BSc) is an Auckland based Nutritionist who specialises in breaking down diet culture, and finding peace with food and your body. She consults with an holistic, non- restrictive approach and allows her clients to tune into their own inner wisdom.