The media promote it, so called “health experts” comment on it and many overweight and obese people swear by it! Yes, a slow metabolism is to blame for societies weight problems, or so it appears. To answer this we need to examine the facts behind what metabolism is and how it affects your weight?

Metabolism is defined as the total sum of all the chemical reactions taking place in your body and is measured in calories. There is a general assumption that someone who is overweight and has difficulty losing weight, must have a slow metabolism, but contrary to popular opinion, someone who is overweight or obese has a GREATER energy expenditure than someone who is thin.

My clinical experience confirms this. The fact of the matter is, the bigger you are the more energy is needed to keep all of your bodily cells (including fat) in balance. Often thin people don’t have faster metabolisms that somehow save and protect them from weight gain, and people with problems losing weight don’t necessarily have a slow metabolism.
Additional to your weight, several other factors also influence your metabolism, such as your build, physical and environmental factors, as well as diseases, medications and smoking habits.

Researchers from the rehabilitation clinical institute, in “Villa Delle Querece”, Italy investigated which of these factors most heavily influenced the metabolism of 57 obese women, with an average age of 52 years. They reported that metabolism was positively related to:

  • Body Temperature
  • Body Weight
  • Height
  • BMI
  • Waist Circumference
  • Mid Arm Circumference
  • Thyroid hormones

In addition, the researchers in this study also reported that age did not show any correlation to metabolism, which is in contrast to other research data which has reported, metabolism may drop by 1-2% per decade, from 20 to 75 years of age. According to these data, it appears age presents a very modest if any challenge to the metabolism.
So why do some people struggle to lose weight, while others don’t? Genetics & lifestyle factors, are among some of the theories, but a slow metabolism isn’t to blame.

As much as we may think we know how much we eat on a regular basis, consistent research and scientific evidence has shown time and time again that even the most conscientious among us tend to consistently under-report our food intake!

Humans are very efficient at gaining weight and keeping it on, this is something many of us find hard to accept. To put the average human’s weight gaining ability into perspective, a weight gain of roughly 20 kilos over the course of ten years would only require you to eat 30-40 calories more than your body needed every day! This would be equal too half of an apple, a plum, a small plain biscuit, a small portion of a rice, or a very small cup of soft drink over your resting metabolic rate and daily physical energy expenditure. A sobering thought, but one of the many reasons so many people gain weight. It really doesn’t take much at all for it to happen.

So the take home message is – know your energy requirements (how many calories I need to eat for my goal weight) be sure to measure your energy intake and then add a moderate amount of physical activity (150 minutes per week or more).
You may be surprised with the results


Hagedorn, T., Poggiogalle, E., Savina, C., Coletti, C., Paolini, M., Scavone, L., … & Donini, L. M. (2012). Indirect calorimetry in obese female subjects: Factors influencing the resting metabolic rate. World journal of experimental medicine, 2(3), 58.

  • Accredited Sport Scientist
  • Accredited Exercise Physiologist
  • MSc. (Exercise Science)
  • Post Grad. Dip (Exercise Rehabilitation)
  • Post Grad. Cert (Diabetes Education & Management)
  • BSc. (Exercise Science & Nutrition)
  • Associate Nutritionist
Dany Williams

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