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How much cardio exercise you should do, and when to do it, is a more complicated question. During extended bouts (over 45 minutes) of moderate to high intensity cardio exercise, your body will gradually increase the percentage of protein (stored in your body as muscle tissue) it uses for fuel. When exercise goes on for 90 minutes or more, the amount of energy provided by protein can be as high as 10-12%, compared to the normal 1-2%. So, doing cardio exercise for longer than 45 minutes at a time may be counterproductive if you are trying to increase muscle mass. The best bet for burning maximum calories without sacrificing muscle mass would be shorter, 20-40 minute bouts of higher intensity cardio exercise; interval training, or High Intensity Interval Training (HIIT) would be ideal.
Timing of exercise and meals can also be important here. The most significant period for recovery from both strength training and cardio exercise is the first two hours after your exercise ends. That’s when your body is really primed to use what you eat to replace the fuel reserves you used up during your workout. If your goal is to add or maintain muscle mass, the best thing you can do soon after your strength workout is to have something to eat—ideally, up to 300 calories with a 3-1 ratio of carbs to protein. A few examples might be: a protein or energy bar, a smoothie (made with fruit juice, yogurt and/or protein powder), yogurt with some fruit, or half a sandwich (peanut butter or turkey, for example) on whole grain bread. Try to do your cardio on different days, or a few hours before or after your strength training, to ensure you have maximum energy available for your strength workout and keep your cardio exercise from using too much protein for fuel. For more details on the topic of losing weight while building muscle, click here.
Is it true that men need to eat more than 1,200 calories each day to avoid “starvation mode?”
For many men, 1,200 calories per day will be too low. Because men typically have more muscle mass than women (a function of higher testosterone levels), men and women who weigh the same will have different metabolic rates and calorie requirements. On average, this difference usually works out to about 250-300 calories per day. Therefore, the minimum calorie requirement necessary for maintaining a high metabolic rate will be closer to 1,500 calories per day for most men, and your SparkDiet program should reflect this. Keep in mind that this is usually the minimum—eating fewer calories will result in other problems collectively known as “starvation mode,” which can also hurt your weight loss efforts. Learn more about “starvation mode” here.