Nutrition

Your Metabolism Isn’t “Broken”

The diet industry is riddled with the classic sales approach of “we have a solution to the problem you didn’t know you had until we told you about it”. 

One of the most egregious fibs dieting “experts” will tell you is that your metabolism is in some way “broken” or “confused”. 

If our metabolism ever became confused or broken, weight loss would be the least of your worries. In fact, you probably wouldn’t have any worries because you wouldn’t be here any longer… 

But what exactly is our metabolism? 

 

Metabolism and you

Human metabolism isn’t simply how we manage our weight but it encapsulates all of the chemical reactions that occur within our body.1 

These chemical reactions are continually ongoing and are responsible for energy production, repairs, respiration and removing harmful waste products. 

Your metabolism isn’t simply one thing — it’s an umbrella term for a countless number of things all occurring continually. 

It’s kind of like the immune system; we see it as this singular system (maybe because that’s easier to visualise) when, in reality, it’s a complex mish-mash of many organs and other components of our body all working in synergy and in a state of continual flux to keep you protected. 

Your metabolism, much like the immune system, is also constantly changing. 

For instance, when you eat your metabolism increases. Why? Well, to break down the foods and utilise the nutrients that have just entered the system. 

Want to know something else cool about your metabolism? We’re constantly storing and breaking down stored nutrients. Fat for example — we’re always breaking down fat somewhere in the body whereas in other places we could be storing it. 

Significant weight or fat loss occurs when this turnover is in favour of fat being broken down and used for fuel as opposed to being stored.2 

This is most readily achieved by sustaining a calorie deficit, but what we eat and the activity we perform also play an important part. 

 

Metabolism doesn’t break… but it does change

Hopefully, by now you understand that “metabolic damage” or “confusion” or even a “broken metabolism” are buzz words for salesy types and not what’s actually happening within our body. 

“But why is it that when I’m in a calorie deficit I’m not losing weight like I’d expect?!” 

Well, there are quite a few reasons for that actually… 

Metabolism won’t break or get confused but it does change. It can speed up, slow down, and adapt to the nutrient intake you’re providing. 

There are a number of reasons why your metabolism may speed up: 

  • Eating more food than usual.3 
  • Eating a diet which is higher in protein (protein has the greatest thermic effect meaning, quite simply, the energy it costs for us to digest and use food that we’ve eaten).4 
  • Having a greater amount of lean muscle mass.5 
  • Changes in hormonal profile (for instance, women’s base metabolic rate increases during menstruation).6 
  • If you exercise (certain types of training, such as weight training, have been shown to elevate metabolic rate long after the activity is finished).7,8 
  • If you consume certain dietary components (the likes of caffeine and capsaicin for example elevate energy expenditure).9,10 

If the goal is weight or fat loss (which may not always be the same thing bear in mind; you can lose weight without it necessarily being fat) then incorporating these strategies (within a calorie deficit framework) would be advised. 

Ultimately, the goal should be to retain as much lean muscle mass, maintaining exercise performance as best you can as well as eating as much as possible whilst achieving weight or fat loss. 

This is how you keep your metabolism on your side whilst achieving that ideal muscular, lean physique. 

On the other hand, there are a number of reasons why your metabolism may slow down, and this is really where a lot of that frustration around dieting comes from: 

  • You’re not eating enough (albeit, you can still lose weight, this doesn’t “shut off” when you reach a certain energy intake threshold it just becomes harder to achieve a deficit thanks to adaptation).11 
  • You’re expending less energy (either through less programmed physical activity or your non-exercise activity which can account for up to 1000kcals of energy expended per day!)12 
  • Your diet doesn’t contain enough protein 
  • You’re losing lean muscle mass from malnourishment and inadequate exercise 

This myriad of mind-numbingly frustrating hurdles to achieve that weight loss you’re aiming for is coined “adaptive thermogenesis”.13 

This essentially encapsulates the behavioural, hormonal, metabolic, and autonomic (your autonomic nervous system is responsible for regulating involuntary body functions, such as heartbeat, blood flow, breathing, and digestion) changes that accompany weight change. 

To put it bluntly, your metabolism hasn’t broken or become confused, your body is simply “fighting back” against the weight loss you’re aiming to achieve. 

We actually covered this topic in another article that you may want to check out. 

 

So, what can we do to fight back against the fight back?

Roll over and play dead? 

Absolutely not. In fact, there’s plenty that you can do to override your physiological response and push through these plateaus and achieved successful and sustained weight loss. 

So, what can we do to actually achieve successful, sustained weight loss?  

Well, firstly, it’d be a lot of what we’ve already covered in elevating your metabolism: 

  • Eating as much as you can whilst losing weight 
  • Eating a diet higher in protein (“actual experts” suggest somewhere between 1.2 to 1.6g per kg of bodyweight per day)14 
  • Continue to exercise and perform intense exercise several times a week 
  • Consider incorporating the likes of caffeine into your diet. 

Well, that’s great for keeping your energy expenditure firing on all cylinders, but what else do we have to do to achieve sustained long term weight loss? 

A group of researchers drew up a large-scale study incorporating over 70 papers which laid out what they discovered were the keys to successful and sustained weight loss.15 

The keys to successful and sustained weight loss were found to be: 

  • Portion control 
  • A reduction in total food energy intake 
  • A higher dietary protein intake (told you so!) 
  • A lower dietary fat intake (not to say dietary fat is “bad” but it is the densest of the macronutrient groups lauding in at around 9kcals per gram) 
  • An increase in plant-based foods (fruit and vegetable intake) 
  • Fewer calories consumed from sugar-sweetened beverages 
  • An inclusive rather than exclusive approach to food choice (food flexibility which, recently, has been shown to be as good during a diet, compared to super-rigid dieting, as well as much better for after!)16 

They also found that those who tracked their weight, monitored their eating and maintained an active lifestyle were found to be generally more successful than those who didn’t. 

One other strategy to avoiding any unwanted metabolic slowdown is planning in “diet breaks”. 

A funky study called the MATADOR study (I’m not fibbing, it stands for Minimising Adaptive Thermogenesis and Deactivating Obesity Rebound) trialled these diet breaks between two groups of weight loss enthusiasts.17 

One group was asked to follow a continuous calorie restriction diet whereas the other was assigned to 2 weeks on, 2 weeks off, alternating calorie restriction and eating at maintenance.  

All in all, the study was fairly lengthy (around 30 weeks of actual dieting) and yielded some interesting findings! 

The researchers found that it was those following the intermittent dieting format who achieved greater weight and fat loss. The researchers believe this was because the diet breaks reduced the impact of adaptive thermogenesis (and that this approach is actually much more sustainable too). 

 

Take home message

Metabolism doesn’t break. 

Nor does it get confused. 

If that actually happened, you’d be not alive enough to care all that much about a few pounds on the scale. 

Our metabolism can change, however, especially when we’re trying to lose weight. 

Adaptations to the size of our body, our body composition, the energy intake we have available and the makeup of our diet all play a factor in our metabolism and whether it speeds up, goes down or stays the same. 

Our articles should be used for informational and educational purposes only and are not intended to be taken as medical advice. If you’re concerned, consult a health professional before taking dietary supplements or introducing any major changes to your diet.


  1. de Nava, A. S. L., & Raja, A. (2020).Physiology, MetabolismStatPearls [Internet]. 
  2. Dokken, B. B., & Tsao, T. S. (2007).The physiology of body weight regulation: are we too efficient for our own good?Diabetes Spectrum20(3), 166-170. 
  3. Poehlman, E. T., & Horton, E. S. (1989).The impact of food intake and exercise on energy expenditureNutrition reviews47(5), 129-137. 
  4. Pesta, D. H., & Samuel, V. T. (2014).A high-protein diet for reducing body fat: mechanisms and possible caveatsNutrition & metabolism11(1), 1-8. 
  5. McMurray, R. G., Soares, J., Caspersen, C. J., & McCurdy, T. (2014).Examining variations of resting metabolic rate of adults: a public health perspectiveMedicine and science in sports and exercise46(7), 1352. 
  6. Benton, M. J., Hutchins, A. M., & Dawes, J. J. (2020).Effect of menstrual cycle on resting metabolism: A systematic review and meta-analysisPloS one15(7), e0236025. 
  7. Poehlman, E. T., & Horton, E. S. (1989).The impact of food intake and exercise on energy expenditureNutrition reviews47(5), 129-137. 
  8. Aristizabal, J. C.,Freidenreich, D. J., Volk, B. M., Kupchak, B. R., Saenz, C., Maresh, C. M., … & Volek, J. S. (2015). Effect of resistance training on resting metabolic rate and its estimation by a dual-energy X-ray absorptiometry metabolic mapEuropean journal of clinical nutrition69(7), 831-836. 
  9. Koot, P., &Deurenberg, P. (1995). Comparison of changes in energy expenditure and body temperatures after caffeine consumption. Annals of Nutrition and Metabolism39(3), 135-142. 
  10. Koot, P., &Deurenberg, P. (1995). Comparison of changes in energy expenditure and body temperatures after caffeine consumptionAnnals of Nutrition and Metabolism39(3), 135-142. 
  11. Müller, M. J., Enderle, J.,Pourhassan, M., Braun, W., Eggeling, B., Lagerpusch, M., … & Bosy-Westphal, A. (2015). Metabolic adaptation to caloric restriction and subsequent refeeding: the Minnesota Starvation Experiment revisitedThe American journal of clinical nutrition102(4), 807-819. 
  12. von Loeffelholz, C., & Birkenfeld, A. (2018).The role of non-exercise activity thermogenesis in human obesityEndotext [Internet]. 
  13. Rosenbaum, M., & Leibel, R. L. (2010).Adaptive thermogenesis in humansInternational journal of obesity34(1), S47-S55. 
  14. Leidy, H. J., Clifton, P. M., Astrup, A., Wycherley, T. P.,Westerterp-Plantenga, M. S., Luscombe-Marsh, N. D., … & Mattes, R. D. (2015). The role of protein in weight loss and maintenanceThe American journal of clinical nutrition101(6), 1320S-1329S. 
  15. Varkevisser, R. D. M., VanStralen, M. M., Kroeze, W., Ket, J. C. F., & Steenhuis, I. H. M. (2019). Determinants of weight loss maintenance: a systematic reviewObesity reviews20(2), 171-211. 
  16. Conlin, L. A., Aguilar, D. T., Rogers, G. E., & Campbell, B. I. (2021).Flexible vs. rigid dieting in resistance-trained individuals seeking to optimize their physiques: A randomized controlled trialJournal of the International Society of Sports Nutrition18(1), 1-10. 
  17. Byrne, N. M., Sainsbury, A., King, N. A., Hills, A. P., & Wood, R. E. (2018).Intermittent energy restriction improves weight loss efficiency in obese men: the MATADOR studyInternational journal of obesity42(2), 129-138. 


Jamie Wright

Jamie Wright

Writer and expert

Jamie Wright holds an MSc Degree in Human Nutrition and a BSc (Hons) in Sports and Exercise Science, and now works with multiple organisations as well as running his own private nutritionist coaching services company, Balance, along with his team of qualified experts, to help individuals with their nutritional goals. He is accredited with the Association for Nutrition and has helped hundreds of clients; from those with eating disorders to internationally competing athletes. Jamie supports his clients with evidence-based, holistic nutrition programming to reach their health and fitness goals. In addition to running his practice, Jamie regularly contributes to the field of nutrition presenting and writing on its many facets. He has had his research presented at the UK Obesity Congress as well as overseas conferences and has authored several e-books whilst contributing to others (including charitable sporting organisations). His research has centred around weight management as well as sports / exercise performance and supplementation. A massive sport nut, avid gym goer and lover of all things dog related, Jamie’s goal in sharing the experience and knowledge he has gained academically and professionally is to provide a source of clarity in the vast amount of “misinformation and noise” that exists within the health and fitness industry. You can check his work out further at Balance, @balance_ie or @jamiesdietguide on social media.


Shop our best sellers and save 30% | Code: FUEL Shop & Save Now!