Daily energy: watch calories, hours of sitting and a stalled scale

Your daily energy expenditure combines what the body uses at rest, everyday movement and workouts. This guide shows how much to trust the calories your watch reports, how to add movement to a desk day and what to check when your weight stops dropping, before taking more food off your plate.

Watch calories: how much to trust them

A watch has no calorie sensor: it combines heart rate, movement, age and weight in a calculation. In 62 young men, 34 minutes of strength training burned 141 kcal measured in the lab, and 4 watches showed on average 146, 258, 299 and 305 kcal; on the treadmill, watches were 9% to 30% above the lab [1]. Heart rate did better, with an average difference of up to 4 beats per minute, although right after a set two models read 20 to 26 beats lower [2].

This is not new: in 2017, none of 7 watches had less than 20% error in calories [3]. In strength training, the lab measurement itself may miss part of the energy used during sets [4].

• Read workout calories as an estimate, especially for strength training.
• Do not decide how much extra to eat from that number alone; watch your hunger and weight over the weeks.
• Use heart rate to track effort and wait a few moments after a set before checking.
• Use the watch to compare movement between weeks.

A desk day, hour by hour: 30 minutes of movement

In more than 1 million adults, those who sat over 8 hours a day but did the equivalent of 60 to 75 minutes of moderate activity daily had no higher risk of death than those who sat under 4 hours [5]. With sensors in 44,370 people, about 30 to 40 minutes per day of moderate or vigorous movement already reduced that association [6]. In a one-day test, 2-minute walks every 20 minutes of sitting reduced the blood sugar rise by 24% to 30% [7], and light movement was also associated with lower risk [8].

That is 20 minutes of brisk walking and 10 of breaks, 30 in total. A brisk pace is one where you can still talk but not sing. Pick one line per week, tie the break to something that already happens, such as the end of a meeting, and if a break every 20 minutes does not fit, start with one per hour.

When the scale stalls: 4 things to check before cutting more

The body saves energy, but it does not shut down. In 71 adults who ate 1,000 kcal a day for 8 weeks, resting expenditure was 92 kcal below predicted; with stable weight for 4 weeks, 38 kcal; at 1 year, 7 kcal, with no clear difference [9]. The brake may be larger after losing a lot of weight, 300 to 400 kcal per day according to a review [10], and 499 kcal in participants of a TV program six years later, an extreme case [11].

Counting in your head also misleads: in 10 people who said they ate under 1,200 kcal without losing weight, expenditure was as expected, and reported intake was 47% below actual [12]. It is not a lack of willpower: measuring is hard.

Eating less tends to reduce daily movement without people noticing, and a review recommends strength training and protein with small cuts rather than large ones [13].

How CatLena uses it

On the Metrics screen, the average energy balance for the period combines what you ate and what you burned, with steps and workouts. In the example below, the average balance was –1,797 kcal per day over 7 days, with 41.5 km run. Looking at the weekly average, not a single day, is the first of the checks above.

When to see a professional