Why doesn't Built With Science use my workout or step tracking data to calculate my nutrition targets?

A common questions we receive is:

"If the app knows how many workouts I'm doing and how many steps I'm taking, shouldn't that affect my calorie targets?"

The short answer is yes, physical activity absolutely affects your calorie needs.

The reason we don't directly use workout or step tracking data is because the calorie burn estimates generated by most wearables and fitness trackers simply aren't accurate enough.

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The problem with calorie burn estimates

Many users assume that devices such as Apple Watch, Garmin, Fitbit, and other fitness trackers can accurately tell them how many calories they burned during a workout.

Unfortunately, research has shown that while many of these devices are excellent at tracking movement and activity, they are often much less accurate when estimating calorie expenditure.

Depending on the device and activity, calorie burn estimates can vary significantly from a person's actual energy expenditure.

As a result, using these estimates directly in our nutrition calculations would often make recommendations less accurate, not more.

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Does that mean exercise doesn't matter?

Not at all.

Every workout, walk, run, sport, and physical activity contributes to your daily calorie expenditure.

In fact, your activity level is one of the biggest factors influencing your maintenance calories.

The difference is that rather than relying on wearable-generated calorie estimates, we use your actual nutrition intake and body weight trends to determine how many calories your body is truly using.

This allows us to account for all forms of activity, whether they're tracked by a device or not.

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Then why should I log my workouts in the Built With Science+ app?

While workout data isn't used to calculate your nutrition targets, it still plays an important role in your overall fitness journey.

Logging your workouts allows you to:

• Track your strength progress over time
• See previous weights, reps, and sets performed
• Receive progression cues for upcoming workouts
• Apply progressive overload more consistently
• Identify plateaus and areas for improvement
• Build a complete training history

For most people, consistently getting stronger is one of the clearest signs that their training and nutrition are working.

Rather than using workout data to estimate calories burned, BWS+ focuses on helping you use that data for what it's most valuable for: tracking performance and making steady progress in the gym.

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Want to learn how the Nutrition Check-In works?

If you're interested in learning how the app estimates your maintenance calories and adjusts your nutrition targets over time, check out:

How does the app calculate and adjust my calorie goal during the Nutrition Check-In?

This article explains how the Nutrition Check-In uses your nutrition logs, body weight trends, and long-term data to generate recommendations.