Humans grow rapidly up to age of 18 and growth halts or progressively halts thereafter. Boys may continue growing in height up to 22 years of age. So there might be still a chance for boys after 20 years. Remember that the height factor depends on the genes you inherit. On the contrary there are other factors which inhibit your growth even though you have inherited taller genes. Nonetheless I will suggest you some tips which may help you in gaining height and adds extra mass to your body implying that you gain weight too.
1. Have a healthy diet. Make sure you have good amount of proteins, Vitamin D, A and C and B complex. You should have sufficient amounts of calcium, phosphorous, iron and zinc in your daily diet. Proteins help you in gaining muscle mass. If you are looking for improving your weight, proteins is the answer. Vitamins help you keep your bones healthy and enhance your growth. Vitamin D and mineral Calcium are two important components that help in maintaining the strength of your bones. Make sure you have all these nutritional values in your daily food. Foods such as meat, eggs, milk, fish, lentils, oysters, oats, citrus fruits, green tea, berries, dairy products, leafy vegetables are rich in nutritional value.
2. Have sufficient sleep. You must sleep at least 8 hours per day. The growth of the body is controlled (other than) by Pituitary Hormone called the Growth Hormone secreted by Pituitary gland. This gland is very active when you are asleep. So have a proper sleep to enhance hormonal functions.
3. Do exercises like jogging, swimming, skipping, stretching and bar hanging. All these workouts will help you keep your body fit and also enhance growth especially bar hanging and stretching exercises. Take a walk in Sunlight, this will make your body to produce more vitamin D which helps in growth of bones. Weighted exercises may inhibit the growth in height. So I would suggest you to do simple exercises without weights.
4. Avoid habits that inhibit your growth such as tobacco or alcohol consumption, improper posture, starving yourself from sleep and unhealthy dietary habits.
A healthy lifestyle will definitely help you in reaching your targets. But remember that don't fall into traps about people advertising about magic pills that will enhance you height. The credibility of those pills is not proved yet. And also remember that height is a multi-factorial quality of human being which is controlled by many factors such as genes, hormones, physical and physiological factors. There is no guarantee that you may grow in height even if you follow all these healthy plans in your daily life. Just follow them and it will keep you healthy nonetheless.
Stay motivated, stay healthy.
Dr. V. Shashikanth