This is the best way to burn fat (and it isn’t hard work)

For so long high-intensity cardio workouts have grabbed all the headlines, touted as the best way to improve overall fitness and boost performance. But I’ve got good news for you: you don’t have to bust a gut to get superfit. In fact, research has shown that exercising in Zone 2, which means at just 60 to 70 per cent of your maximum heart rate, allows you to build a strong aerobic base, unlocks higher-level performance gains, enhances your endurance and… drumroll… makes your body use up its fat reserves far, far more efficiently. Yet despite its ability to transform our health, leanness, energy levels and performance it is perhaps one of the most overlooked forms of training. Let me explain how it works and what it can do for you.

What exactly is ‘Zone 2’?

Technically you are in Zone 2 at the point at which you are able to sustain your work rate working aerobically without significant feelings of strain, breathlessness or that point at which you feel muscles becoming heavier with lactic acid. On a scale of one-to-10 exertion, it’s a six, so it’s very moderate.

If you are walking or cycling, to stay in Zone 2 you need to stick to one level of terrain. This is because otherwise your heart rate will rise and fall, the energy demands on your body will rise and fall with it, and you will stray out of the zone. People often find a stationary bike or rower works well, while for many people running on a treadmill often produces higher heart rates even when running slowly.

What are the benefits?

Injury prevention, faster recovery, higher performance and body-fat reduction are all benefits of working out in Zone 2. One of the key reasons for this is the effect that sustained and regular training has on our mitochondria, which are the main energy producing engines housed within each one of our cells. The healthier and more abundant your mitochondria, the more efficient your body is at responding to demands that we throw at it.

Stay with me. The crucial part is coming up: while working out at Zone 2 levels our mitochondria use fats as their main source of energy, rather than sugar reserves used when exercising more intensely.

The greater the number and the healthier the mitochondria in your cells, the more fatty acids are burned and the longer you can sustain activity without resorting to using your body’s sugar, which is the more readily available but less desirable source of energy. A low volume or dysfunctional mitochondria is a sign of poor health, metabolic problems and in more extreme cases even disease. What we are aiming for is a body that more readily burns fat, and relies less on burning sugar. 

In fact, our health is defined by how our body uses fat vs sugar – Type 2 diabetes being the most obvious and common example of dysfunctional energy usage becoming a life-threatening problem. 

We need to be lean enough to be healthy and increase our chances of extending our health and lifespan. On the one hand our bodies need to be able to easily turn fat reserves into energy through the day to keep us going. However we do also need the flexibility to be able to respond to increased physical demands as they happen and use glucose – aka sugar – appropriately when needed too. 

Zone 2 training prepares your cells and mitochondria to have the energy flexibility that will allow just that. In fact, Zone 2 training will also increase your ability to perform at high intensities. 

So what do you need to do?

Four times a week, you need to work out for a minimum of 40 minutes of sustained duration at 60 to 70 per cent of your maximum heart rate. This is Zone 2. There are many ways of calculating your maximum heart rate, the most basic being the sum of 220 minus your age. The easiest way is using a fitness tracker, which will obviously also measure your heart rate as you exercise, ensuring that you remain at the correct level of exertion – which you will of course have worked out in advance. For maximum benefit it should be kept within a very small heart-rate band so try to do activities that do not stop and start and do not deviate too greatly. 

You could be fast walking a dog but be conscious of not stopping and starting when they do as this allows your heart rate to fall. You can be on a cycle ride but keep it on flat terrain. You can row, but only if you can keep going for 40 minutes plus. Bottom line, you can do pretty much any cardiovascular exercise you like, as long as you can sustain your heart rate at the correct level for the length of time required. This isn’t to say that you are simply substituting high intensity for low: I’ll be coming back to how, when and why to use high intensity in future columns. But this moderated approach will get you where you need to go faster. 

While this might seem like a big ask in terms of time spent over and above other workouts you do, the gains overall are simply enormous. We are supposed to be continuously active for long periods in our day, Zone 2 training reflects that and your body will thank you for many more years to come.