How your workout changes today's calorie target
A workout makes Burnie add active calories to today's maths, so your 'Remaining' number jumps up. The honest move is to eat back only about half of it, or nothing at all. Here is why, with the real numbers.
You just finished a workout. You feel great. You open Burnie. The 'Remaining' number has jumped up. It looks like today just handed you extra food. So can you eat all of it back? This short read is the honest maths behind that little bump.
A workout adds less than your watch says
Two honest reasons. First, your watch's calorie number can be quite wrong. In a big Stanford test of seven wrist trackers, not one kept its error under 20 percent. The best was still off by about 27 percent. The worst was off by 93. Second, even a true burn is not all 'extra'. A dietitian puts it simply. If you burn 100 calories in a workout, your whole-day burn only goes up by about 70. The other 30 you would have spent anyway, just staying alive. That is your BMR doing its job. So a '250 kcal' workout on the watch may be only about 175 extra for the day. That gap is the whole story.
What 30 minutes really earns (70 kg adult)
Eat back every calorie your watch says you burned.
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Your watch's number is gross. That means it counts calories you would have burned anyway, just breathing and staying warm. A dietitian explains: burn 100 in a workout and your whole day burn rises by only about 70. On top of that, the watch can over-read by 20 to 93 percent. So eat the full number back and you eat more than you earned. The deficit you worked for quietly melts away into an extra roti or a sweet chai. The maths turns against you.
If you eat back, use the conservative 50% rule
The bottom line
Your workout does bump today's calorie number, but by less than the watch shows. Trackers can over-read by 20 to 93 percent, and about 30 of every 100 burned calories you would have spent anyway. So eat back about half, or nothing at all. Log the snack first, drink water, and let the rest widen your deficit. The walk is for your heart and your mood. The deficit is for the scale. Burnie never reads your heart rate, sleep, blood pressure, or location, so you stay in charge of the maths.