Why the calorie in/ calorie out method of weight management is flawed

By BodyMatters psychologist Sarah McMahon

Yep, it sounds simple. You eat less and exercise more, create a calorie deficit and lose weight. It makes sense for anyone who has done Year 1 maths. However this oversimplified idea is extremely dangerous because it completely undermines the complexity of the body.

Working with people who have eating disorders or a long history of dieting, we see daily proof that the calorie in/ calorie out method of weight management or weight loss is flawed. Too often we see clients who are eating far less than their body requires  and not actually losing weight. Usually this is extremely distressing for them because they believe there is something wrong with their bodies- and not the calorie in/ calorie out myth. So four reasons why this method is flawed:

One: It forgets that our bodies actually do need energy for daily functioning

Have you ever wondered why so many people maintain their body weight without exercising or without worrying about what they eat? It is because a large amount of the energy we consume is allocated to keeping our body functioning. Sleeping, thinking & participating in life all uses energy. The calorie in/ calorie out method completely forgets this.

Two: It ignores one vital element: Our metabolism!

Your metabolism is how your body processes everything you eat & drink- converting sugar, fat & protein into energy. Most people don’t know much about the metabolism, however it is one of many highly intelligent systems in our body. Our metabolism combines two distinct processes, anabolism & catabolism:

  • Anabolism is where energy is created & stored. It is known as your “constructive metabolism” as it supports the growth of new cells, the maintenance of body tissues, and the storage of energy for future use. During anabolism, small molecules are changed into larger, more complex molecules of carbohydrate, protein & fat.
  • Catabolism is when energy is released. It is known as your “destructive metabolism” as it breaks down food components (ie carbohydrates, proteins and fats) into simpler forms to create energy required to release energy. This provides the fuel for anabolism.



There are a further four elements that make up or metabolism:

  • Our Basal Metabolic Rate (BMR), which is our resting metabolic rate, and represents the energy we would burn when our body is at rest. It is the amount of energy our body needs to maintain itself. It fuels our brain, heart and other important organs. The speed of our BMR It is determined by lean mass, particularly lean muscle mass (specifically, the proportion of muscle you have is likely to determine a higher metabolic rate). Anything that reduces lean muscle mass will also reduce our BMR. We can roughly calculate our BMR, which usually accounts for 50 to 80% of energy that is metabolised.
  • The thermic effect of food. This is the energy we use to eat, digest and metabolise food. Our metabolism rises after we eat because we use energy to eat, digest & metabolise the food we’ve just eaten. So eating actually increases our metabolism. This occurs soon after you start eating and peaks after about two to three hours following eating. The thermic effect of food increases our metabolism between 2-3% and up to 25-30% depending on the size of the meal and the type of food. When we skip meals or severely reduce the number of calories we eat, our body compensates by slowing down our metabolism, allowing it to save calories for energy our body will need to handle its basic functions. It is also one of the many reasons why, to recover from an eating disorder, it is valuable to engage in mechanical eating of 3 meals & 3 snacks, all 2-3 hours apart.
  • Physical activity. This is how much energy is burnt during movement. Physical activity typically accounts for about 20% of energy expenditure, however this of course can increase with additional movement.
  • The Injury factor. This is the energy required to repair the body following injury, as well as other issues such as pain and stress.

In addition to all of these, our metabolism is also influenced by other factors, including our age (metabolism naturally slows about 5% per decade after age 40); sex (men generally burn more calories at rest than women); and heredity.

Three. It ultimately leads to weight gain

The calorie in/ calorie out is based on a system of averages that ignores the complexity of digestion. As aforementioned, it doesn’t consider our own metabolism and the factors that may vary that. It also doesn’t consider the metabolic properties of food. So while following the calories in-calories out method may result in some initial weight loss, ultimately it serves to slow down our metabolism and accelerate weight gain in the longer term. This is because our body, in it’s wisdom, takes a reduction of energy seriously and slows down our metabolism to maintain the homeostatis of our body weight. It doesn’t  know that we are in 2014 and “thin is in”. Our body is only concerned about our biological well being.

We know that diets don’t work.  Cofounder Lydia Turner has also written extensively on the vicious cycle of weight loss that trying to lose weight actually maintains, simply because food restriction leads to weight gain in the longer term.

Four. It is a prescription for disordered eating.

There are many problems that people approach psychologists for to seek help, the theme with what determines whether a problem is “clinically significant” is when it impacts on daily functioning. Worrying about our weight is a phenomenon of the 21st century and beyond- and ironically the more we as a culture have worried about what we are eating the fatter we are becoming. No doubt this is due to the fact that we are trying to micromanage a system that was actually designed to take care of itself! Our body has many examples of this and I have previously written about how we need to retrain ourselves to pay attention to these messages rather than ignore them.

Ultimately counting calories and making decisions on what we eat based on this is disordered. Not only does it undermine our body and our metabolism, it impacts on our ability to function in the world in a free and happy way. In the same way, excercising to burn calories- and counting them in the process- takes us away from the pleasure of that experience and is far more likely to result in us not continuing with exercise in the longer term.

One response to “Why the calorie in/ calorie out method of weight management is flawed

Leave a Reply

Your email address will not be published.

This site uses Akismet to reduce spam. Learn how your comment data is processed.