It’s eating fat that makes you fat, new mouse study suggests
Worldwide obesity has tripled since 1975, with 1.9 billion adults considered overweight. The condition now kills more people across the globe than underweight and malnutrition.
One of the NHS’s biggest cost burdens, a staggering 70% of UK adults are expected to have overweight or obesity by 2034. Obesity is a problem of energy balance. If a person has more calories coming in than are going out, then the difference is generally stored as body fat. But what needs to be identified are the factors causing the imbalance of intake and spending in the first place. Why don’t humans have a control system that allows them to eat exactly what they need and no more? Understanding the answer to this question may help tackle the obesity epidemic.
There have been several explanations of why people sometimes overconsume calories. These generally revolve around the macronutrient composition of our diets. Macronutrients consist of fats, protein and carbohydrates. One explanation for over-consumption of calories is called the protein leverage hypothesis. The idea is that we primarily eat food for its protein content.
If the amount of protein falls in relation to the amount of fat and carbohydrate, then to meet our protein needs we overconsume calories.
An alternative is the carbohydrate-insulin model. This maintains that it is carbohydrates that make us fat, because when we eat them they stimulate the production of insulin, which promotes storage of the carbohydrates as fat and stimulates hunger to procure additional intake. This idea has become very popular in the wake of several books that have spawned the whole “high fat-low carb” (HFLC) diet movement.
The classic idea, however, is that what makes us fat is eating fat, because fat stimulates reward centres in our brains that encourage us to overeat. This has been called the hedonic over-ride hypothesis.
Obesity-related conditions include heart disease, stroke, type 2 diabetes and certain types of cancer that are some of the leading causes of preventable, premature death.
John Speakman
Chair in Zoology, University of Aberdeen