Your body burns a variety of fuels during workouts, including stored fat, carbs and sugar. Typically, your body switches back and forth between these types of fuels depending on the intensity and condition of the activity.

Heart rate can be an important tool in determining the right intensity for your workouts, which can help you achieve your weight loss goals. But, as cardiologist Nieca Goldberg notes, there’s no one-size-fits-all formula.

Fat Burning Zone

Getting your heart rate right can make a big difference in your fitness and weight loss goals. Using heart rate zones to guide your workouts can help you burn more calories, and reach your fitness goals quicker, says NASM-certified personal trainer Anthony Baugh.

But how do you know which heart rate zone is optimal for you? There are several charts and equations available to find out your target cardio heart rate, known as your fat burning zone.

The Fat Burning Zone is a lower-intensity area of exercise in which the body uses stored fat as fuel. This may help with weight loss, but it’s not the most effective way to shed fat.

Ultimately, it’s the amount of calories burned that determines how much weight you lose. The body is better at using stored glycogen (carbohydrates) as fuel in higher-intensity exercise, explains cardiologist Nieca Goldberg, MD.

High Intensity Zone

When you’re in the High Intensity Zone during a workout, your heart rate is quickened to about 70-80% of your maximum heart rate. In this zone, your body taps stored fat for energy.

During this workout, your body is more likely to burn fat than it is to burn carbohydrates. This is because fats have a higher energy density than carbohydrates and can be easily broken down into a form your body can use more quickly.

While your diet should be the primary factor in your weight loss, any type of physical activity that elevates your heart rate will help you burn calories and lose weight. But if you’re just starting out, it’s best to stick to the moderate or low end of your target heart rate zone so you can ease yourself into a fitness routine.

Moderate Intensity Zone

The Moderate Intensity Zone (60-69 percent of your Max Heart Rate) is a great way to train your general endurance. You can sustain this intensity for a long time, and it helps you to make cardiovascular gains over time.

This is also known as the aerobic zone, and it’s where your body uses a mix of fuels during exercise. You may feel tired and a little dizzy, but it’s an effective and safe way to improve your endurance.

You’ll want to focus on this zone for the longest amount of time possible to see a significant increase in your weight loss cardio heart rate. The moderate zone is a good place to start if you’re new to physical activity or are recovering from a break.

Your target heart rate is based on your maximum heart rate (MHR), which is calculated by subtracting your age from 220. Once you know your MHR, you can use the chart below to plan workouts in each of Myzone’s five training zones.

Low Intensity Zone

The Low Intensity Zone is a good place to start your weight loss cardio workout. You should keep your heart rate in this range for longer periods of time to help improve your endurance and take your body into fat-burning mode.

In lower-intensity exercise, the body uses fat for energy because it’s easier to break down than carbs. However, when you’re exercising at a high intensity, your body needs energy more quickly and must turn to carbohydrates.

During this period, your muscles use glycogen, a stored sugar that’s more easily broken down than fat. The problem is that glycogen doesn’t store as much energy as fat does, so your body has to find other sources of fuel.

Using a fitness tracker can help you determine your target heart rate and ensure you’re in the appropriate intensity. Many fitness trackers will also provide you with a zone to work in, based on your age, gender and fitness level.