Originally Answered: how can i build muscle mass if i have a very high metabolism?
You do not have a very high metabolism. You have been punked by a stupid myth and your metabolism is fine. Google "metabolism" and study a bit.
Your problems are (a) you're only 15 and (b) you may be a near ectomorph. You have ten years before you will have your lifetime max of the muscle building hormone testosterone so relax. It's going to be a while. In the mean time, study and use books, not dot coms on the internet. Even if you can't add much muscle because of your age and the fact that you may be a "late bloomer", you can prepare for the day when you don't have that deficit. Now, here's the ectomorph story.
If you're an ectomorph (very thin/skinny) or near ectomorph you will have difficulty gaining weight because of your somatype, not because of metabolism. So, if you wan to change that and add some pounds there are two ways to do it. Both may work and neither may work. Your success is going to ultimately depend on your body chemistry which is inherited (genetic).
The difference between naturally fat and naturally thin people is the number of fat cells in their body. An endomorph may have as many as 250 billion adipocytes (fat cells) while the ectomorph may only have about 50 billion. There's no way to change your total adipocytes or their distribution throughout your body. How fat or thin you are has almost nothing to do with metabolism.
You can try adding fat by eating more food. You should eat a proper diet which is about 50/20/30 (%calories from carbs/fats/protein respectively) and just consume more food. You should NOT eat junk food, increase your carbs, take supplements, consume more fat, etc. Just eat a proper, well balanced diet in increase the portions (serving sizes). If you are able to add body fat, you will have no control over where the fat goes or how it looks. In other words, the result could be "skinny fat" which is probably less appealing aesthetically than skinny. And, of course, if you don't like the fat, you'll just have to lose it to get back to where you were.
You can try adding muscle. It is always good to try to add muscle because muscle is the best metabolic investment you can make. Here are some of the benefits of strength training.
• Stronger bones & increased mineral density (osteoporosis protection)
• Stronger body & musculature (improved protection from injury)
• More robust organic and systemic fitness (more survivable in crisis)
• Improved cardio-vascular function (better than "cardio")
• Higher basal metabolic rate (~5-50 cal/day/pound of muscle)
• Easier fat loss (more efficient lipid consumption)
• Greater calorie consumption (prolonged afterburn)
• Supports body sculpting (hypertrophy)
• Slows natural loss of muscle mass (sarcopenia) over age 30
Adding muscle is a very slow and difficult process. Watch this video for more about that ---> http://www.youtube.com/user/scooby1961#p... . On average males can add no more than about a pound of muscle per month and females can add about 20% less and that is only under ideal circumstances which are rare. However, if you're a teen, you may find adding muscle to be almost impossible because you will not have your lifetime maximum of testosterone (the muscle building hormone) until about your mid20s.
Adding muscle means very intense (and painful) training for a few hours per week and usually requires a gym or gym facilities. It also requires some understanding of how to train (exercise physiology, kinesiology, muscle anatomy, etc) which usually means some time spent with a personal trainer. Adding muscle is a difficult and long term process and, once the muscle is added, the training must continue to maintain the muscle.
Ectomorphism is an unhappy an occurrence because being very thin can effect self esteem and inhibit social interaction. However, the ectomorph will usually, in adult life, find it easier to achieve and maintain an ideal or close to ideal body weight because people naturally tend to grow fatter and/or more robust as they grow older....especially with proper diet and training. In other words, being underweight now may be paying it forward. You may reap the benefits with a nice body while your midlife peers are fighting the battle of the bulge.
Note - Do not use pills, tonics, supplements, shakes, or other products which claim they can help increase body weight without first checking with your doctor. The scammers are very much aware of the plight of the ectomorph and there are scores or companies with products and advertising all designed to capitalize on your misfortune for their profit. Don't be a sucker.
So, they may not be ideal. But those are your two options. Fat and/or muscle.
Now, read this --> http://www.eatright.org/Public/content.a...
Good luck and good health!!