Metabolism is a big word people throw around without a true understanding of what it is, how it is affected and how to control it to your advantage. Hopefully todays blog will give you some insight into metabolism so we can move away from the over used excuse of

“I can’t lose any weight…. I have a slow metabolism”


So what exactly is my metabolism?

In simple terms a collection of chemical reactions that take place inside the bodies cells. Metabolism is responsible for converting the food we eat (fuel) into the energy we need to power everything we do. This includes movement, activity, and growth, to using our brains to function throughout the day.

Our bodies operate in two different states as we constantly strive to live in a state of equilibrium (homeostasis). The two sides to this homeostasis include catabolism cellular destruction (the process that produces the energy required for all activity in the cells) and anabolism cellular regeneration (supports the growth of new cells, the maintenance of body tissues, and the storage of energy for use in the future).

How is metabolism affected?

So if we look at calories being a unit of how much energy a particular food or meal has we can determine how much energy a particular food/meal will provide our body. As with any dietary approach if the body has a surplus of energy it’s classed as constructive metabolism (anabolism). This means the body has adequate fuel to repair and fuel the body beyond its normal requirements. Alongside this we see an according and supporting rise in both the anabolic and metabolic hormones. In direct contrast when in a calorie deficit, we see a rise in catabolic hormones initiating the process of destructive metabolism. This is where the body will break down its own stores of metabolites as fuel.

“This all seems logical and a simple equation right? If I just consume less calories my body will lose weight and if I consume more calories I will put on weight”.

Unfortunately it’s not just that simple! In a calorie deficit the body has intelligent ways of adapting to preserve homeostasis shown through the body’s metabolic adaptation response. This decreases energy expenditure, improves metabolic efficiency and increases cues for energy intake to maintain survival. Metabolic adaptations, which occur during weight loss, include adaptive thermogenesis, increased mitochondrial efficiency and hormonal alterations favouring a decrease in energy expenditure, decreased satiety and an increase in hunger. These adaptations may cause the individual difficultly in dietary adherence and make further weight loss difficult despite lower caloric intake and higher physical activity levels.

How do I use metabolism to my advantage?

Here come the trade offs. When in a hyper caloric state we run the risk of fat gain however in a hypo caloric state we run the risk of lean tissue loss. Therefore we must understand that any chronic or long-term period in which either state becomes detrimental to physique goals.

Therefore a strategy for fat loss or muscle gain must be put in place for example weight loss in humans (i.e. a net oxidation of stored substrates) requires total ingested energy (over a period of time) to be less then total energy expenditure, resulting in a loss of body weight comprised of stored lipid and lean tissues in a ratio of about 3:1 (Phillips, 2014).

When weight loss occurs rapidly the ratio shifts towards greater lean tissue loss even in athletic subjects. When determining an appropriate caloric intake, consideration of preserving lean body mass must be prioritized. The size of the energy deficit will affect how much of the weight loss comes from lean body mass, thus weight loss that is gradual is preferred for lean body mass retention (Helms, Zinn, Rowlands, & Brown, 2013).

This gradual and varied caloric intake/deficit has implications for macronutrient intake. Finding the optimal macronutrient balance is of high importance for the individual during calorie restriction. If one macronutrient is set too high it will force another too low potentially resulting in decreased performance outcomes (Helms et al. 2013).

Best practice for fat loss or muscle gain should be achieved through a strategy of quantifiable periods of time where the individual is required to sit above or below the hypothetical line of homeostasis. This should be achieved via a strategic decrease or increase in caloric intake combined with intense strength training (Helms et al. 2014).

If you are interested in finding the best metabolically efficient way to achieve your body composition goals with calorie requirements and macronutrients tailored and adjusted to met the requirements of your body please get in contact with me at


Further Reading

Helms, E., Zinn, C., Rowlands, D., & Brown, S. (2013). A systematic review of dietary protein during caloric restriction in resistance trained lean athletes: a case for higher intakes. Int J Sport Nutr Exerc Metab.

 Helms, E., Aragon, A., & Fitschen, P. (2014). Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation. Journal of the International Society of Sports Nutrition, 11(1), 20.

 Phillips, S. M. (2014). A Brief Review of Higher Dietary Protein Diets in Weight Loss: A Focus on Athletes. Sports Medicine (Auckland, N.z.), 44(Suppl 2), 149-153. doi:10.1007/s40279-014-0254-y


Hannah Sweetman – Online Nutrition Coach & Elite Coach



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