Is it okey to drink whey protein even if you dont go to gym?

I would be careful with that. It depends on how much he drinks of course. Protein derived from whey is the best kind of protein you can get. However, if your husband is not a body builder, drinking lots of whey protein a day means that you consume a lot of excess protein that's not needed in your body. This excess protein could potentially cause stress on your liver because the liver has to break down a certain part of protein constantly. I say everything in moderation is good. If he has a high metabolism I was told that peanut butter is helpful?..

sure you can still drink it but you should only drink it when you are using up lots of energy or have high metabolism its easy to burn off the calories.

Yes you can gain weight with out going to the gym but you can not build muscle with out working out. If your husband does not get enough protein in his body from eating then it will not hurt him, however if he eats a lot of meats and is taking protein shakes as well without working out, he will be putting too much protien in his body.

I wouldn't advise you to give him whey protein. I found that many people have a hard time digesting it, you said you felt sleepy after the drink... that's because it take alot of energy to digest milk proteins. There's a reasons why he's too lazy to eat, I can't tell you what it is as I don't know him personally and how do he eat but generally the main reasons for lack of apetite are:

1- Stress, anxiety or any others emotionnal problems.

2- Endocrinal(hormonal if you prefer!) or digestive problems

3- Some medications

4- Some health conditions like cancer, HIV, etc...

5- Habituating to eating less

You first need to find if it comes from one of these reasons then you can use some nutritionnal strategies.

Firstly, the key is to eat easily digested quality proteins! My recommendation is to take spirulina, it's the best source of protein as well as being high in vitamins and minerals, it's perfect for picky eater! Other superfoods high in protein, like chlorella, hemp seeds, goji berries, etc. are useful.

Secondly, eat high calorie foods like nuts and seeds, avocado, dates, coconut(it may be in the form of coconut milk) etc...

Be sure to include good quality fats like flax oil, olive oil, hemp seeds, nuts and seeds, avocado, etc.

The last but none the least point is exercise! That's critical for weight gain! Depending on how thin he may be... don't make him start doing exercise if he's looking anorexic and under eating!

I hope that helped!:)