by increasing your calories
I'd recommend a weight gainer and eat 3 full meals a day, each meal should equal to 800 cals was +
By eating too much when you are stress.
Calorie counting for either weight loss or weight gain is the way too go
Increase your appetite by keeping doing those weights lifts... Then eat!!! eat and eat, there's no miracle solution.
make smoothies put chocolate or peanut butter or take a mass gainer
Foods to eat if you have hyperthyroidism
Low-iodine foods
The mineral iodine plays a key role in making thyroid hormones. A low-iodine diet helps to reduce thyroid hormones. Add these foods to your daily diet:
non-iodized salt
coffee or tea (without milk or dairy- or soy-based creamers)
egg whites
fresh or canned fruit
unsalted nuts and nut butters
homemade bread or breads made without salt, dairy, and eggs
popcorn with non-iodized salt
oats
potatoes
honey
maple syrup
If you want to gain weight, it’s very important to do it right.
Binging on soda and donuts may help you gain weight, but it can destroy your health at the same time.
If you’re underweight, you want to gain a balanced amount of muscle mass and subcutaneous fat rather than a lot of unhealthy belly fat.
There are plenty of normal-weight people who get type 2 diabetes, heart disease and other health problems often associated with obesity (11Trusted Source).
Therefore, it’s absolutely essential to eat healthy foods and live an overall healthy lifestyle.