“You Can’t Out Run A Bad Diet” True Or False?

by Barney St Anton in Nutrition

food | diet | personal trainer

“You can’t out run a bad diet” True or False?

Time and time again I have said in these blogs that the most important thing for weight loss is to create a caloric deficit. In essence, eating less and/or moving more. However at times it can be confusing whether or not this should come from altering your dietary intake, increasing physical activity levels or a combination of both. In this blog I will explain why I believe altering your dietary intake is the most important aspect for weight loss, but why increasing physical activity levels is also crucial for improving health.


It’s important to consider the role of energy expenditure in energy balance. As stated above, one way of creating the energy deficit required to lose body fat could be to increase your physical activity levels. Physical activity accounts for 15 – 30% of energy expenditure and is the only component of energy expenditure that is influenced by behaviour in the short-term.

Furthermore, there is some evidence to suggest that there may be a limit to how much energy can be burnt in one day. Research tracking the daily activity of Hadza tribe hunter-gatherers in Northern Tanzania using GPS systems found they either walked or ran almost all day from sun rise to sun set excluding a break in the shade at mid-day. Despite the tribes extremely high levels of physical activity total calories burnt throughout the day was not much higher than those who live a sedentary and modernised lifestyle such as in the U.K. or U.S.A. Whilst the reasons behind this phenomena remain unclear there is a suggestion that the body may compensate by reducing metabolic function.


Your dietary intake has a strong link with your rate of weight loss and intake does not appear to have as strict a limit. Hormones such as Leptin and Insulin are responsible for regulating appetite however, intake is dictated by behaviour. Motivation and determination can help work through those tough days.

This research questions the effectiveness of relying solely upon exercise as a means to create the energy deficit required for weight loss.

I want to make it very clear that I’m not saying exercise is NOT important and should be avoided. Instead, we should change our views from thinking that diet and exercise are 2 interchangeable tools and really understand how they can help us. It’s clear that your rate of weight loss is mostly related to your dietary intake, exercise has a number of benefits that include stimulating muscle mass, enhancing bone mineral density and improving blood pressure. Both should be used combined alongside one another to effectively reduce bodyweight whilst improving health.

On balance, both are important but it may be that exercise is more important for improving health factors whilst diet is best for improving body composition by losing body fat mass.

  • The saying “you can’t out run a bad diet” may infact be true!
  • Put equal effort in to your diet as you do in your classes/gym sessions and adopt a new healthy lifestyle.