Nils Behrens: Does the Apple Watch fool you about the calories?

The self-experiment with the watch on the wrist

The fascination was great: Finally a watch that apparently shows exactly how many calories are consumed daily. 3,200 kcal here, 3,600 kcal there – numbers that suggest everything is in the green zone. However, those who rely on this and eat accordingly often experience a surprise. Instead of a defined figure, a gain around the waist often follows.

This paradox shows: Smartwatches like the Apple Watch motivate, but they do not calculate like a nutritionist or a sports physician.

What science says about fitness trackers

The enthusiasm for wearables has gained enormous momentum in recent years. Millions of people worldwide rely on the numbers that their wrist spits out daily. However, numerous studies show: The calorie counts should be taken with caution.

• A review in the British Journal of Sports Medicine (Fuller et al., 2020) shows that fitness trackers overestimate energy consumption by 20 to 90% .
• Even the Apple Watch, which performs comparatively well in tests, is on average 27% above actual consumption, according to a study by Stanford University (Shcherbina et al., Journal of Personalized Medicine, 2017).
• The data is particularly unreliable for strength training and everyday movements, where the algorithms only inaccurately represent the actual metabolism.

The result: Those who apply the displayed values one-to-one to their diet regularly eat more than they actually burn.

Nils Behrens, Chief Brand Officer of Sunday Natural and host of the podcast HEALTHWISE

Why the Apple Watch is still valuable

Despite its limitations, don't underestimate the Apple Watch. Its potential lies less in exact calorie counts, but more in motivation and transparency.

1. Motivation and Routine: The daily "closing of rings" motivates you to stay active consistently. Consistency is a critical factor for healthy longevity.
2. Trends over individual values: Even if the absolute number is incorrect, trends are reliable. Seeing your activity increase over weeks helps develop a better sense of progress.
3. Heart rate tracking: Smartwatches are very precise here. Heart rate variability (HRV), resting pulse, and training intensity can be well-read—all important markers for resilience, recovery, and longevity.

Longevity doesn't start with the watch, but with habits.

For healthy longevity, it is not crucial whether a watch displays 2,800 or 3,500 calories. What matters is the long-term balance of exercise, nutrition, recovery, and mental stability.

1. Exercise: More daily steps, targeted strength training, and moderate endurance training are proven to be the most effective means against age-related muscle loss and metabolic slowdown.
2. Nutrition: A balanced diet with proteins, fiber, omega-3 fatty acids, and micronutrients is more sustainable than relying on numbers from the wrist.
3. Recovery: Sleep quality and stress reduction affect lifespan at least as much as calorie consumption. Smartwatches help make patterns visible, but they do not replace a healthy routine.

Conclusion: Your path to smart longevity

The Apple Watch is a great tool if you categorize it correctly. It provides impulses, makes progress visible, and supports self-reflection. However, anyone who believes the calorie display is a precise basis for dietary calculations is mistaken.

Use the watch as a motivator, not as a dietary guide. For your longevity, this means relying on proven principles – exercise, balanced nutrition, recovery, and meaningfulness – and seeing the watch as a valuable companion, not as the sole authority.

Nils Behrens is the Chief Brand Officer of Sunday Natural and host of the podcast HEALTHWISE. The sought-after health expert also teaches as a lecturer at the Fresenius University of Applied Sciences. Previously, Behrens worked for over 12 years as Chief Marketing Officer of the Lanserhof Group and host of the successful "Forever Young" podcast.

Here you can find all columns by Nils Behrens