The idea that snacking frequently throughout the day can significantly boost our metabolism has long been a popular notion, but recent expert commentary suggests this may be little more than a myth. Driven by the assumption that eating regularly will kickstart calorie burning, many of us have fallen into the trap of overeating or grazing throughout the day, convinced it's essential for weight loss and improved metabolic health.
However, says Professor James Betts, a professor of metabolic physiology at the University of Bath: 'When people talk about metabolism, they're usually referring to their metabolic rate – the total amount of energy their body expends over a given period.' This rate is largely influenced by factors like age, sex, size and body composition, which are relatively fixed. But understanding what drives daily energy expenditure can help debunk common myths.
The human body burns calories from three main sources: resting metabolism – the energy required for basic bodily functions; processing food; and physical activity. 'Physical activity is by far the most variable and controllable aspect of our daily energy output,' Professor Betts explains. He notes that resting metabolism, which accounts for a significant portion of daily calorie burn, is highly predictable and can be estimated accurately based on factors like body weight, age and sex.
Regarding frequent eating, Professor Betts clarifies that while digesting food does require some energy (around 10% of the calories consumed), it's not substantial enough to offset caloric intake or provide a significant boost to overall metabolism. He likens this 'thermic effect of food' to a 'tax on the food consumed': if you eat 100 calories, you'll gain around 90 net calories because 10 calories were invested in processing the food.
For those aiming to increase their total energy expenditure, Professor Betts offers clear advice: 'Move more.' This strategy is far more effective in burning calories and impacting metabolic rate than relying on frequent eating schedules. The research findings align with broader scientific understanding in metabolic physiology, providing practical guidance for public health.