Does sweating more help you lose more fat?

Short answer

No. Weight lost through sweat is water that comes back when you refill, and exercising in a sauna suit burned only 23 kcal more.

Does sweating more help you lose more fat?
'More sweat → lower weight → less fat' — does this formula hold?
Running in a sauna suit or training in the heat makes the scale drop fast, so it looks like fat is melting. That is why many people believe a workout only counts if you sweat a lot. We checked whether the lost weight is really fat.
20 minutes in a sauna lowers your weight
3-0.4 kg without moving
674 people lay in a dry sauna for two 10-minute sessions, and their weight dropped by a median of 0.3 kg in women and 0.4 kg in men. That weight came off while lying still, with no exercise. The researchers treated the loss as the amount of fluid to drink back.
Weight lost fast comes back fast
Fighters regained 7-9% before the bout
Among 2,100 combat-sport athletes and boxers who cut weight quickly before weigh-ins, body weight went back up 7-9% between weigh-in and the fight. For a 70 kg (154 lb) person, that is 5-6 kg returning in a short time.
Does a sauna suit burn more calories?
Only 23 kcal more
12 people did the same interval workout once with a sauna suit and once without. With the suit they burned 285 vs 271 kcal during exercise and 123 vs 113 kcal in the 1 hour after, about 23 kcal more in total. That is roughly 6% of the total.
Heat makes you burn more carbs, not fat
At 40°C, muscles used more stored carbs
12 people cycled for about 40 minutes at the same effort at 40°C and 20°C. In the heat, their muscles burned more stored carbohydrate (glycogen). Hot conditions raise body temperature and stress hormones, shifting fuel use toward carbs rather than fat.
What about hot yoga?
Calories per hour matched 23°C
When 16 people did the same 1-hour yoga sequence at 40°C and 23°C, calories burned did not differ. In a study where 52 people did yoga 3 times a week for 12 weeks, the 40.5°C group ended with lower body fat percentage than the 23°C group, but a hotter room did not burn more calories.
Bottom line: weight lost to sweat is water
Fat loss follows calories burned, not sweat
The 0.3-0.4 kg lost in 20 minutes of sauna was water to replace, and 7-9% of rapidly cut weight came back before the fight. A sauna suit added only 23 kcal. Judge a workout by total calories burned, not by how much you sweat.