How Much vs What We Eat and Weight Gain

October 8th, 2021 | Posted in Info

How Much vs What We Eat and Weight Gain

It’s well known that how much we eat affects our weight. However, it may be more complicated than a simple calories in vs calories out equation. This month’s blog posts will look at how what we eat and when we eat may affect weight just as much as how much we eat.

How Much vs What We Eat and Weight Gain

In the UK in 2019-2020 there were nearly 11 thousand hospital admissions directly attributable to obesity and just over 1 million hospital admissions where obesity was a factor. Weight is a big problem in this country and the Western world.

It’s long been believed that people gain weight when they consume more energy than they expend. This is known as the energy balance model. However, this may be an over-simplification.

The energy balance model has been the main weight management strategy employed by governments and health workers for decades. It states that weight gain is caused by consuming more energy than we expend. Given that we live in a world where many of us can consume as much as we like while expending very little energy it’s easy to eat more calories than we need and this certainly has an effect on weight. However, despite decades of public health messaging encouraging people to eat less and exercise more rates of obesity have steadily risen.

All Calories Are Not Equal

The energy balance model doesn’t take into account the fact that the body does not deal with all calories in the same way. A new study suggests that obesity is, at least partly, a metabolic disorder caused by eating too many refined carbohydrates and their effect on insulin. The authors of the study believe that the carbohydrate-insulin model better explains obesity and weight gain (1).

Carbohydrates and Insulin

When we eat highly processed carbohydrates they break down into glucose rapidly in the gut. This glucose goes into the blood stream causing a dramatic spike in blood glucose. In order to bring this glucose down to a safe level the body secretes insulin to carry the glucose from the blood into the cells. However, if insulin levels keep surging the cells become deaf to it and more has to be produced in order to get the glucose into the cells. Having regular high levels of insulin leads to more of the glucose being converted into fat for storage on the body. At the same time there is less glucose available to fuel the muscles and other metabolically active tissue meaning energy may be low despite eating a high energy diet. The brain perceives that the body isn’t getting enough energy, which, in turn, leads to feelings of hunger. In addition, metabolism may slow down in the body’s attempt to conserve fuel and we may remain hungry, despite gaining fat.

What to Avoid

The carbohydrate-insulin model suggests that reducing consumption of rapidly digestible carbohydrates reduces the storage of glucose as fat leading to weight loss and less hunger.

The key is to avoid sugar and ultra-processed foods – these are foods that contain ingredients that you would not have in your kitchen cupboard at home. Instead aim to cook from scratch as much as possible.


The carbohydrate-insulin model claims that overeating isn’t the main cause of obesity. Instead, it suggests that the obesity epidemic is largely caused by dietary patterns characterised by excessive consumption of high glycaemic load foods, particularly processed, rapidly digestible carbohydrates. These foods cause hormonal responses that change our metabolism, leading to fat storage and weight gain. This puts the emphasis on what we eat rather than how many calories we eat.  If this way of thinking were adopted by health workers and policy makers it could lead to more effective, long-lasting weight management strategies being more widely adopted.

See also blog posts on When to Eat and The Gut Microbiome and Weight for more information about weight and dietary patterns.


1. David S Ludwig et al. The carbohydrate-insulin model: a physiological perspective on the obesity pandemic. The American Journal of Clinical Nutrition, 2021