Why it’s diet – and not exercise – that’s key to weight loss.

Why it’s diet – and not exercise – that’s key to weight loss.

What’s more important for losing weight, what you eat or how much exercise you do? The spotlight has always been on how much exercise we should do to lose weight, but real change comes from what you eat. We tend to associate being ‘in shape’ with working hard at our physical fitness. We expect that working up a sweat is our payback for indulging in ‘naughty’ foods, that the reason we’re overweight is because we’re not active enough. 

While it’s true that being sedentary is bad for our waistlines, science has some unfortunate news for you if you’re banking on losing weight by continuing to eat rubbish and working it off at the gym. Weight loss is more down to what you eat than how much exercise you do.

Exercise is still a good thing

Let’s just take a moment to say that despite focusing on the importance of your diet, exercise is still extremely good for you. We’re certainly not telling you to ditch your trainers. 

Exercise is important for our overall health, and it has a whole host of benefits for both body and mind. It can help to reduce your chances of type 2 diabetes, stroke and heart disease, and is thought to help with depression, so you should definitely continue to exercise.

But when it comes to losing weight, it’s just not as important as what you eat. What you eat has a much bigger part to play in weight loss. 

Calories in vs calories out

When explained at its very simplest, weight loss comes down to the balance of energy we take in vs the energy we expend. So if you take in more energy (i.e. calories from food) than you expend (i.e. calories burned from activity), you’ll gain weight. Expend more energy than you take in and you’ll lose weight. 

If you want to lose weight, you’ll need to create a calorie deficit, ensuring that the number of calories you burn a day is greater than the number of calories you consume. You burn calories in a number of ways – through normal bodily functions, activity such as fidgeting and moving around during the day, and through exercise. 

There are two ways of creating a calorie deficit. You can either reduce the number of calories you take in, or increase the number of calories you burn.

While it’s definitely possible, in theory, to create a substantial calorie deficit through exercise alone, it’s harder to do it this way than through what you eat.


Feel the burn

You’ve heard of the phrase ‘you can’t outrun a bad diet’, right? It sounds like a Pinterest board, but it does have some truth behind it. If your nutrition isn’t great, then no amount of running will help you lose weight.

As anyone who has ever attempted to ‘burn off’ a slice of cake will know, it takes a really long time to burn a meaningful amount of calories through exercise. If you’re aiming to create a calorie deficit, it’s a lot easier to just not have that slice of cake rather than punish yourself afterwards with hours of cardio. 

There’s also the impact exercise has on our appetites to consider. Have you ever done a particularly vigorous workout and then felt like you wanted to eat everything in sight? It’s a common theme, and while it can be seen as ‘refuelling’, when we’re talking about calories in vs calories out it’s just another way of taking in a lot of extra calories with very little effort. 

Exercise also has a knock-on effect in our daily lives known as ‘compensatory behaviours’. This means you might take the lift instead of the stairs because of a particularly strenuous leg day, or you might want to rest more because you’re tired.

Both scenarios are completely understandable, but it means that you won’t be burning the calories you’d usually burn by using the stairs or being generally more active. 

So what’s the best way to lose weight?

While it’s possible to lose weight without moving a muscle, the best way to do it for long-term success is to find a combination of eating well and exercise that works for you. That means striking a good balance between being a couch potato and fretting over burning every last calorie. 

You might’ve heard the 80/20 theory, which is that weight loss is 80% eating and 20% exercise. It’s not a hard and fast rule, but generally this is a good balance to aim for.