Which matters more – diet or exercise?

Emma Brown - Nutritionist | 17 May, 2022

We all know that following a healthy diet AND regular exercise are both important for long-term health and reaching or maintaining a healthy weight. The question is, which of these is most important – or put it this way, which is most impactful?

The saying goes 'you can't outrun a bad diet' – which pretty much sums it up. While exercise is hugely beneficial for overall health and can help with weight maintenance, if you don't manage your diet and ensure you stick to a healthy calorie intake, exercise can only help so much.

Let's look further into why this is the case and the roles diet and exercise play in weight loss and overall health.

Weight loss

weight loss

To lose 1lb per week, you need to create a 500 calorie deficit per day. This can be achieved through eating less or moving more, or a combination of the two. So the question is – is it best to eat less or move more?

For most people, consuming 500 fewer calories each day is much more realistic and sustainable than trying to burn off 500 calories per day. Think about how easy it can be to eat 500 calories – grab a large milky coffee and a slice of cake and you're there. But to burn off 500 calories would, for example, require us to do one of the following:

  • Run at 6mph for 60 minutes
  • Swim front crawl at a moderate intensity for 60 minutes
  • Do a vigorous spinning class for 40 minutes

On top of this, the physical demand of burning an additional 500 calories through exercise each day is pretty big. Unless you're a full-time athlete, not many of us could commit this time every single day. We also need rest days from exercise to allow our body time to recover, so burning this number of calories each day through activity would not be sustainable.

Another consideration is the impact lots of exercise has on our appetite. Doing a significant amount of exercise every day can make us feel hungrier which could mean we end up eating more calories and cancelling out some of the calorie burn. Not to mention there is evidence to suggest that many people subconsciously eat more when they're being very active as a way to compensate for the extra energy used (1).



What about when it comes to our health? There's no denying regular exercise is extremely beneficial to our overall health. It helps to strengthen and improve our cardiovascular health, bone density and muscle strength to name a few, as well as boosting our overall mood and sense of well-being.

Research has also shown that individuals who are overweight can significantly improve their health through regular exercise, even in the absence of any weight loss (2). What we find is that regular physical activity can help improve various elements of our health from better blood sugar control, to reduced cholesterol, and even improvements in mental health. This shows how important exercise is in isolation, regardless of weight status.

But is exercise alone enough to counteract poor dietary choices?

Sadly, it doesn't seem so. There is anecdotal evidence that even very active, healthy-weight individuals can suffer the health consequences of an unhealthy diet (3). There are cases of individuals who run miles and miles each week and maintain a healthy weight, but indulge in a diet rich in saturated fat, salt and sugar, who suffer with health issues related to poor diet such as heart disease and diabetes. It's even been reported that as much as 40% of people with a healthy body weight may have some level of metabolic abnormality (4). This again highlights the importance of a healthy diet on overall health status.

Conversely, a well-balanced diet which is also calorie-controlled to help maintain a healthy weight is proven to benefit our health. Eating a diet rich in important nutrients such as protein, fibre, good fats, calcium and other vitamins and minerals, but low in saturated fat, free-sugars and salt, helps to ensure our body receives all the nutrients it needs to function at it's best, without burdening it with excessive amounts of less desirable nutrients.

Winning combo

While diet is coming out on top in terms of importance, a combination of a good diet and regular exercise is definitely the way to go when it comes to health and weight loss.

So in summary, my advice is to focus on a balanced diet with a suitable calorie allowance for weight loss (or maintenance), while taking part in regular physical activity to help boost your weight loss progress and benefit your health long term.

Nutritionist Emma Brown (ANutr), MSc Human Nutrition is passionate about how food science applies to the human body, and how the nutrients in what we eat affect us and ultimately have an impact on our health.