Putting a sweater on when it's cold out is probably a good idea. But wearing one in the gym in an attempt to burn more calories is not. You'll risk dehydration.
Does Wearing a Sweatshirt While Running Burn More Calories
Working Out in a Hoodie: Benefits, Reasons & More
Burn Calories on Leg Day
Can Waist Belts Make You Lose Weight?
Why muscular endurance is important if you want to burn more fat
Is It Unhealthy to Use a Sauna After a Workout?
Exercising in the heat: Do you burn more calories?
How many calories do you burn while running?
Lifting weights vs. cardio: Which burns more calories?
How Many Calories Does Swimming Burn?
Is a good sweat necessary for a good workout?
Exercises for Weight Loss
Calories Burned Weightlifting: Maximize Fat And Calorie Burning
Choosing the Right Workout Clothes
How Many Calories Should You Burn During a Workout? Experts Weigh In