With dieting trends such as dry January, the paleo diet, the Atkins diet, the keto diet and phrases such as “you are what you eat”, one could be forgiven for thinking that diet is all there is to it when it comes to managing your weight. However, is this really true?

In our article “Overweight does not always mean unhealthy“, we explored the possibility that we are putting too much emphasis on one type of measure to judge health and fitness when in reality, while weight plays a role in overall health, one can have a larger body and still be considered fit and healthy.

Increasingly, scientists are saying that an approach focused on weight loss may be misplaced when it comes to obesity management. Instead, they suggest that a “fat-but-fit” approach based on increasing physical activity levels and improving cardiorespiratory fitness should be the primary focus for those looking to lose excess body weight.

Proponents of the fat-but-fit approach to obesity treatment argue that improving fitness, even in the absence of weight loss, can help reduce the risk of cardiovascular disease and mortality.

The journal iScience has recently explored how to reduce the risk of obesity-related health conditions and mortality. It compares the effectiveness of physical activity and cardiorespiratory fitness with that of weight loss.

Physical activity refers to any movement that results in energy expenditure while cardiorespiratory fitness is a measure of overall physical fitness. Cardiorespiratory fitness measures the ability of the cardiovascular and respiratory systems to sustain physical activity over an extended period.

According to evidence presented by iScience, the fat-but-fit approach may be at least as effective as weight loss in reducing the risk of cardiovascular disease and mortality due to obesity. Furthermore, this fitness-focused strategy avoids the pitfalls of the weight loss approach.

While some studies show that intentional weight loss through calorie restriction and physical exercise can reduce mortality risk, others show a lack of association between weight loss and mortality risk. In other words, the research has not consistently shown that weight loss reduces mortality risk.

Advice for weight loss generally involves restricting calorie intake alongside increasing physical activity levels. Thus, in studies reporting a reduction in mortality risk associated with weight loss, an increase in physical activity may account for this finding rather than weight loss itself.

It is also important to recognise and acknowledge that sustaining weight loss over a prolonged period is often challenging. As more individuals attempt to lose weight by reducing calorie intake, there has also been an increase in the prevalence of weight cycling.

Three recent meta-analyses suggest that weight cycling is associated with increased risk of cardiovascular disease-related and all-cause mortality. Weight cycling is losing weight and regaining it over and over. It’s called “yo-yo” dieting when it happens because of dieting.

In contrast to weight loss, there is more consistent evidence suggesting that cardiorespiratory fitness can greatly attenuate or even eliminate the mortality risks associated with high BMI.

For example, some studies have indicated that cardiorespiratory fitness could significantly reduce all-cause and cardiovascular disease-related mortality risk associated with high BMI. Furthermore, fit individuals with excess body weight had a lower risk of all-cause mortality than unfit individuals with a weight in the healthy range.

Follow-up studies also show that increasing physical activity levels and improving cardiorespiratory fitness can reduce mortality risk associated with BMI in the long term.

Moreover, improvements in cardiorespiratory fitness and physical activity tend to produce a larger reduction in mortality risk than weight loss.

Notably, a number of these studies show that these effects of physical activity and improved cardiorespiratory fitness accompanied either modest or no weight loss. This indicates that it is not possible to attribute the reduced all-cause and cardiovascular disease-related mortality risk associated with improved fitness to weight loss.

This could mean that while weight loss should not be discouraged, there should also be a corresponding focus on improving fitness when it comes to obesity management.

As Dr. Glenn Gaesser, a professor at Arizona State University says “Current obesity treatment guidelines do not even mention ‘fitness’ and only encourage physical activity as a means to facilitate weight loss. This approach ignores the major improvements in mortality and disease risk associated with increased physical activity and improved fitness in the absence of weight loss. In fact, as our review shows, improving fitness by increasing physical activity is associated with greater reductions in mortality risk compared to weight loss.“

*This article does not replace professional medical advice