A guy of 19 ,5'9 of height,49 of weight, Asian. My first attempt to Gain weight after Being dumped By my Ex. The reason: i am too thin. Need help.
Do you want muscle, or fat? If you want fat, it could be easy. If you want muscle, it'd be more challenging.
First of all, start tracking your calories. Use something like MyFitnessPal or one of the many alternatives, but always double-check entries with the nutrition labels on food, or for whole foods nutritiondata.self.com, which is an excellent database for those. There's a lot of very inaccurate and downright wrong entries on trackers where the users supply the data.
With the tracking, you'll find out how much you really eat. It's possible it ain't as much as you think. If you chow down something like 3000 kcal per day and yet don't gain any weight, given your height, maybe check with your doctor. Conditions such as hyperthyroidism could affect your metabolism. Maybe you have difficulty actually taking up the nutrients.
If you eat what seems like a normal amount for your body mass, and medical conditions are excluded, it's time to eat more. You might've tried this, and found it hard. So focus on foods that go down easy but can pack good calorie density. Full-fat milk, if you're not lactose-intolerant, can be consumed throughout the day in place of water and can provide 600+ kcal per liter. Fat is the most calorie-dense of the macronutrients, and particularly oils are some of the richest foods known. Quality olive oil would be a good choice to keep things from getting excessively unhealthy. Carbohydrate-rich foods digest quickly, so if you're not gluten-intolerant and digest carbs well, large portions of pasta would help. Need some sauce on it? Pesto is very high in calories, owing to the aforementioned olive oil and pine nuts. Nuts and seeds are very nourishing too.
Would you like to gain more lean mass and keep the fat in check? Then resistance training with heavy weights is your best bet. Find beginner programs that utilize linear progression and focus on the heavy compound lifts: squats, deadlifts, bench press, overhead press, pull-ups, rows, perhaps some explosive movements like power cleans. Starting Strength and StrongLifts 5x5 are popular choices. You'll need to consume a substantial amount of protein. Chicken and turkey are good sources but can be quite lean. Using cuts (or the whole bird) with the skin on ups the fat content. You might want to look into protein supplements. They may seem expensive, but some math will show you that unless you go for the overpriced isolates (simple whey or egg protein will do) the price per gram of protein will be quite a bit lower than when getting it from whole food sources. Mixes perfectly with the full-fat milk. Keep in mind they're supplements, though. You'll still need quality food besides them to get a complete micronutrient profile.
People tend to make fun of the GOMAD idea in Rippetoe's book Starting Strength. GOMAD stands for "gallon of milk a day" (or about 3.7 liters). However, it's his way of showing people who claim that they just can't gain weight that it is most definitely possible in the absence of serious medical conditions. If you can digest it, drinking a gallon of whole milk each day, every day, on top of what you normally eat, will result in weight gain. If it doesn't, see your physician.