I'm underweight and I don't know what to do about it.

I have pretty much the same issue. I'm way too skinny. I eat a lot of junk food like ice cream and cookies and chips and stuff like that and it helps a little.

 

Get yo'self some dark leafy greens and nuts (Nuts and nut butters are very calorie dense! ), foods high in protein will probably do the trick.

Eating highly processed foods such as ice cream and cookies is not a healthy way to gain weight! Find some whole foods you really like

 

Nuts and other proteins are good, like mociaddict suggested. Also try eating more smaller meals through out the day instead of 3 big ones. I have trouble putting on weight too and smaller meals seemed to help. Also, the healthier I eat the more weight I gain, oddly enough.

 

If it makes you feel better,I have a BMI of 14.5

 

Hi I'm very similar, 6'0.75", and have weighed 135-145 since I was 15 (11 years ago). I am now FINALLY starting to gain a little weight (hoping for curves actually!).
A couple tips I've learned:

1) Find your Basal Metabolic Rate with account for how active you are usually. It's how many Calories you need to sustain your weight. Gaining 1 pound takes 3500 Calories EXTRA. For me, to gain 1 pund in a week, I have to eat 2780 Cal per day. That's a lot. That brings me to...

2) It's all about when you eat and what. Fast carbs (simple sugars, bleached flour, etc) are made to burn fast and can spike your blood sugar, and then insulin (as a counterbalance). Messing with high blood sugar is risky, and weight gained will not be good for you (high risk of diabetes too). It is super important to eat at the same times every day. Part of having a stupidly-fast metabolism (mine being an example), the body is basically saying "I have no idea when I'm gonna get another meal, so I'll process everything as fast (not as best) possible!". Eating at normal times trains your digestive system to calm down off panic-mode. As far as what to eat goes: Like others have stated, eat foods high in protein. I find simply peanut butter to be super-high in Calories (just be careful of the sugar content). Rice is another simple to make food that packs high Calories; 1 cup of rice (before cooked) provides me almost 1/4 of my daily Calorie intake need, for example. Also, high-fructose corn syrup is majorly difficult for the human body to process (it is far more saturated and intense than naturally occurring sugars), so avoid it!

3) If you smoke or drink coffee, try to stop. Stimulants, like nicotine, caffeine, even cannabinoids (THC, CBD, etc), speed up metabolism, that is, they send your body the message "burn through all the energy you got, now!". I am in process of quitting smoking, and am otherwise drug-free and sober I already get hungry more. (For me, I am on Estrogen, which is also getting me hungry more often.)

Sorry if I sound geeky, but I hope this info helps.

 

Cal Teen bars

 

I am also underweight! I am 5'3 and 90 pound. I have try eating every food i could get my hands on and just gain a little. I would recommend looking for a nutritionist or eat lots of protein and gaining muscle.

 

Yeah pretty much this. Personally If I were you I wouldn't focus on getting bigger but on getting in shape which means a good diet (Not carbs, empty calories or things that will keep you thin or burn easy), and work on gaining muscle instead of burning calories (Raw cardio will not be the only solution, it's good here and there but it can be overdone).

Beware, this may mean that you end up eating like mad crazy and you've got to diet it right; eating like 10x the amount of something that you eat now could be bad and end up messing with your system, things like messing with your cholesterol level real bad (I knew a guy who ended up hospitalized because he ate like 3+ eggs every day).

Really it's best to consult a nutritional and actually do what they want to you do to, which to be honest is difficult if you don't make and shop for your own food.

Make a plan and stick to it, I don't care if that means hanging signs on your door as you get up in the morning.