Role of Intensity
Intensity is one of the essential components of a workout plan. The American College of Sports Medicine (ACSM) advises that your intensity should be moderate to vigorous whenever you exercise to see benefit. But intensity is also personal. What may be challenging to you may be easy for someone else, and vice versa. You need to evaluate how you feel when you are walking at 2.8 mph for 30 minutes. If you feel like it's easy, you're not working hard enough to burn significant calories for weight loss. Instead, weight loss will be slow or may plateau altogether.
Duration of Workouts
ACSM further advises you about the duration of workouts for general health, and for weight loss. To lose weight you need to accumulate at least 150 minutes or more of moderate to vigorous exercise each week. So 30-minute workouts five days per week will show some weight loss for most people. For more significant weight loss of over 5 percent of your body weight, accumulate 225 to 420 minutes each week.
Calories Burned During Exercise
To lose 1 pound of fat you need to burn an extra 3,500 calories above and beyond what you normally burn. It sounds like it shouldn't be that hard, but it can be. A 160-pound person can burn approximately 204 calories per hour walking at 2 miles per hour, or up to 314 calories in one hour by speeding up to 3.5 miles per hour. The heavier you are, the more calories you will burn because your body needs to work harder. So if you weight 160 pounds you will burn about 157 calories in one 30-minute session walking at 2.8 mph. Do this five times per week and you lose less than a quarter of a pound.
Tips and Considerations
Calories burned are estimations, not set in stone. If 2.8 mph is challenging and you weigh more than 160 pounds, you could burn a lot of calories in 30 minutes. Consistency and frequency of workouts are as important as intensity and duration. One session a week is not going to help you lose weight. Once 2.8 mph gets easier, and it will, increase your speed by 0.1 or 0.2. Each increase will help you burn calories and lose more weight.