The maximum number of calories that can be burned in a day depends on the workout activity that you participate in and the duration. To burn the most calories, participate in the most effective activity for as long as safely possible.
Maximum Exercise Duration
The American College of Sports Medicine recommends a maximum daily exercise duration of 90 minutes, which they say may be necessary for those interested in losing body fat.
Most Effective Exercise
According to MayoClinic.com, running is the most effective calorie-burning physical activity. A 150-lb. person burns about 986 calories running for 60 minutes at a speed of 8 mph. If that person ran for 90 minutes, they would burn a total of approximately 1,479 calories.
Losing weight requires you to create a caloric deficit by burning more calories than you consume. You can maximize the number of calories you burn by running for 90 minutes, but you can also help create more of a caloric deficit by limiting your intake. Eating low-calorie foods will support your weight loss efforts.