No matter where calories come from in a diet, weight is gained or lost by taking in more or fewer calories then the body burns. If more calories are taken in than burned there will be a net gain in body weight. An individual may feel, look and actually be leaner while body weight remains the same or actually increases, especially if resistance training is being done. This is usually due to gains in lean mass and a reduction in body fat. Because of this, the weight scale is not a good indicator of actual lean body mass to fat mass ratio.
Exercise is critical to healthy sustainable weight loss.
All exercise places energy demands on the body increasing calorie expenditure. Either type of exercise will facilitate weight loss if daily caloric expenditure exceeds daily caloric intake. The recommended frequency of aerobic exercise bouts is two to no more than three times a week. The use of low impact aerobic exercise equipment or walking instead of running will theoretically minimize loss of lean muscle tissue in the legs. Keep in mind that it is impossible to spot reduce.