How Does Resistance Training Impact Percent Body Fat?

To make a dent in unwanted body fat, you may think you need to do hours of cardio each week. But if you really want to improve your body composition and change the way your body looks, feels and functions, resistance training is a better choice. Weight training will not only reduce your body fat, it will make you stronger, improve your appearance, increase your bone density and help you perform better throughout the day.

  1. Body Composition

    • Body fat percentage is a ratio of fat mass to fat-free, or lean mass. Your body composition has important implications for health, and provides an important tool for measuring progress when you are trying to lose weight or accomplish fitness goals. According to exercise scientists Len Kravitz, PhD and Vivian Heyward, PhD, ideal body-fat percentage values for optimal health range from 10 to 25 percent for men, and 18 to 30 percent for women. For optimal fitness, men should strive for 12 to 18 percent and women should aspire to a range of 16 to 25 percent. Athletes tend to range a few percentage points lower than fitness values.

    Increased Lean Mass

    • Weight training can have a significant impact on your body composition by increasing your fat-free mass, which includes muscle, bone, vital organs and other body tissue that is not fat. Even if you don't lose a significant amount of fat, increases in your lean muscle mass from resistance training will alter your ratio of fat to lean. Because lean muscle is metabolically active tissue, adding more muscle will raise your basal metabolism and increase the energy demands of your body throughout the day. Provided you don't ingest more calories, the increased metabolic activity will result in a caloric deficit that will help you burn unwanted body fat, further lowering your total body-fat percentage.

    Decreased Fat Mass

    • It is often believed that aerobic exercise is needed to significantly reduce fat mass. But a 2006 study published in the "Journal of Applied Physiology" found that resistance training for 45 minutes resulted in significant fat recruitment and reduction of abdominal fat, and greater overall improvement in subjects' body composition, compared to a sedentary control group. What's more, an increase in fat metabolism continued for 40 minutes after the resistance-training sessions. Another study published in the "Journal of Strength and Conditioning Research" found weight training to be highly effective for improving body composition in overweight and obese children.

    Increased Bone Density

    • Bone mineral density is often overlooked as a significant marker for fitness in younger adults. But the bone density you build in your youth can protect you from osteoporosis that leads to brittle bones and a high risk of fractures later in life. Weight training provides load-bearing activity that can positively impact bone mineral density. Even older adults can benefit from a progressive resistance-training program, which can significantly increase bone density and lean muscle mass, and decrease body-fat percentage. Weight-training programs for older adults should be supervised, and progression should be gradual.