Diet or exercise: what's more important for weight loss?

Obesity and modifiable lifestyle factors 

The obesity epidemic is on the rise around the world, and levels of obesity have tripled globally since 1975. According to the World Health Organisation, most of the world’s population live in countries where overweight and obesity kills more people than underweight.(1) 

This epidemic is largely due to changes in our environment, from increasingly sedentary lifestyles and ease of access to fast and ultra-processed foods. Diet and exercise are two modifiable lifestyle factors which can significantly impact our energy balance. There is considerable research in the field of diet, exercise and weight management, however it appears that there is no “one-size fits all” approach. In fact, there is debate amongst scientists regarding the optimal energy and macronutrient values to promote healthy and sustainable weight loss. 

Low-fat and low-carb

The general consensus used to be that low-fat diets were the ultimate key to weight loss, and for many years health professionals prescribed them to obese individuals. However, such diets have been questioned and challenged for their effectiveness. In fact, one might wonder, if fat intake has decreased, why is the prevalence of obesity showing no signs of slowing down? 

Over recent years, very low carbohydrate, ketogenic diets have gained mass popularity amongst those looking for a quick-fix approach to weight loss. In fact, the very nature of a ketogenic diet promotes short-term weight loss. For many dieters, this initial weight loss can serve as a great encouragement in what can often be a long and challenging journey. However, there is still a lack of long-term safety and efficacy data regarding ketogenic diets. 

Both clinical and anecdotal evidence over the years has shown that weight loss can be achieved through a myriad of dietary interventions.These include the not-so-healthy (e.g. crash diets) and the more sustainable, long-term lifestyle approaches (e.g. the Mediterranean diet). 

From fads to the future of personalised regimes

Exercise is also known to have positive effects on weight loss and overall health, although there are differing schools of thought concerning the most effective type, duration and intensity of exercise. Moreover, weight management plans, whether they involve dietary intervention, exercise, or both, must be sustainable in order to ensure long-term results. 

In fact, far too many fad diets and exercise regimes may work in the short-term. However they are unsustainable and often unhealthy, and if carried out indefinitely, many adherents end up regaining the initial weight lost. 

One of the most exciting fields of research today is that of personalised medicine. This will potentially help to accurately predict individual responses to diet and exercise in the future. This will enable individuals to find the best solution tailored to their individual needs.(2) 

The benefits of exercise 

Exercise has multiple health benefits, from improving cardiovascular function to warding off depression and anxiety . It comes as no surprise then that it’s also an important part of achieving weight balance.

In fact, Michele Olson, professor of physical education and exercise science at Auburn University, Alabama, states that while it is possible to lose weight through dietary intervention alone, exercise is also an important part of the process.Losing weight without exercising is likely to lead to a loss of muscle rather than just fat. Indeed, exercising stimulates muscle growth so losing weight through exercise means you are burning more fat. 

It’s important to note that weighing yourself can also be triggering for some people, especially for anyone who has gone through or is currently going through an eating disorder. A better way to measure weight loss in such cases is to check how your clothes fit, this can give you an indication of changes to your body without having to worry about a number. 

Moreover, exercising to balance weight is not about running marathons or completing triathlons. Dr. Olson suggests starting small and ultimately building up to five to seven weekly workouts, of roughly 50 minutes each and of moderate intensity. She cites brisk walking and zumba as good examples. So even if it’s an hour long vigorous walk with your dog, that still counts as exercise! 

However it’s not just cardio exercise which shows benefits. In fact, resistance training can help too. Body weight exercises such as planks, squats and lunges are all great movements you can practice without any equipment at all. 

Overall, not only will exercise help with weight loss if that’s your objective, it will also have other benefits on your general health from boosting mood to increasing sleep quality. 

Related reading

• Why am I not losing weight on keto? Your keto questions answered.
• How to naturally lose weight during menopause

It all starts in the kitchen 

Whilst exercise is certainly a useful component of weight loss, it goes hand in hand with nutrition. In fact weight loss is generally 75 per cent diet and 25 per cent exercise. Although this is a rough generalisation, it is true that for most people, it is easier to reduce energy consumption than it is to burn energy. 

In other words, it’s easier to adapt your diet to eat less calories than it is to spend hours at the gym each day! For example the average person may burn 600 calories during a 1 hour run, but one large muffin and a latte can easily amount to the same number of calories if not more. 

It’s unsustainable to have to match your exercise levels to your calorie intake in order to obtain a deficit through exercise alone. In addition, it promotes an unhealthy mentality which only sees food as calories, when in reality it’s much more than that. It’s not just about burning off the calories you eat, it’s also about the nutrients that food provides for your body. In fact, as the saying goes, “you can’t out-exercise a bad diet”. 

Calories in vs calories out