Are you one of those people who goes to the gym and keeps training until your body can’t take it anymore, with unbearable muscle pain because you believe that’s the only way to lose fat? If that’s you, there’s something you should know: you’re doing it wrong. The renowned doctor and longevity expert Sebastián La Rosa has revealed on his YouTube channel that this is one of the big mistakes people commonly make, and that if you want real changes in your body both physically and internally, the key isn’t in repeatedly performing high‑intensity workouts (HIT) that leave you wrecked, but in mastering the famous ‘Zone 2’.
Many people mistakenly believe that to lose fat you have to end up completely exhausted and sore, but the reality is that the human body doesn’t operate that way. As Dr. La Rosa warns, “The vast majority of us think incorrectly that if we’re going to exercise—whether we run for an hour, go to the gym, or engage in any activity that burns energy—we are burning fat… Unfortunately your body doesn’t work like that.” The secret lies in the intensity of the exercise you perform: when you train gently or moderately, such as during a brisk walk, the body starts to use the stored fat as its main energy source; conversely, when you perform high‑intensity workouts, the body begins to burn more carbohydrates, as it seeks to burn something quickly to obtain energy. For this reason, the expert recommends using the 80/20 rule, which means spending 80% of the time on a moderate, comfortable workout, known as the ‘Zone 2’, and reserving only 20% for high‑intensity sessions.
What is the ‘Zone 2’ and how to identify it?
The Zone 2 is a level of moderate cardiovascular exercise where your heart rate stays between 60% and 70% of your maximum capacity. In this state, your body begins to draw energy from fat, making it a powerful ally for weight loss. That said, it’s still necessary to combine it with some more intense exercise. Still, the clinician offers an unfailing trick to determine if you’re working in that zone: “It’s an intensity that allows you to have a conversation with a companion, with effort, but doable. Think of it as if you were on a phone call and you couldn’t hide from the other person that you’re exercising.”
For an average person, performing between 45 and 50 minutes of ‘Zone 2’ about three times per week is more than enough to see spectacular results in cardiovascular health and fat loss.
Why do we also need the 20% of HIIT?
If Zone 2 is so beneficial for fat burning, it’s natural to wonder why we shouldn’t do it all the time, but the reality is that we need to combine it with intense exercise due to a substance called lactate (or lactic acid), which is what causes that burning sensation in the muscles after a workout. The gentle training of Zone 2 helps your body become accustomed to producing less of this lactic acid and to using fat much more efficiently as energy, while HIIT drives the body to produce a lot of this acid to then “teach it to clear it” and eliminate it quickly during rest periods. By pairing the two types of exercise you make your body far more efficient and thus goals come faster, since not only will you lose fat, but you’ll also gain more energy.
Beyond the physical, Dr. La Rosa emphasizes that our physical condition is the most important factor in determining how many years we will live and how good our health will be. To measure this, there is a benchmark called VO2 Max, which simply indicates how well your lungs, heart, and muscles manage to utilize oxygen each minute during exertion. To illustrate its importance, the doctor recalls a large study that tracked 750,000 people over 22 years and notes that “the group with the highest VO2max and most training had four times lower risk of death from any cause (…) ranging from cardiovascular diseases to tumors.”
To know what state your body is in today, the doctor proposes two very easy tests that anyone can perform for free. The first is the Cooper Test, ideal for people under 50 or those who can run, and it consists of finding a completely flat path to run the greatest distance you can for 12 straight minutes; the key here is that if you cover less than one and a half kilometers, that’s a signal to alarm that you should start moving.
The second option is the 2-kilometer walking test, designed for older individuals or those who cannot exert themselves as much, where you simply walk that exact distance as fast as you can but without running, guaranteeing that at least one foot stays on the ground at all times. At the end of this walk, you just need to note the time it took and count your heart rate to easily determine how your endurance and aerobic health are doing.
