You'll need to add more high calorie and high fat foods to your diet -- more raw nuts and raw seeds, coconut and avocado. You also want to make sure you're eating healthy foods like brown rice, which are high in calories. When I was a personal trainer, I had a client who couldn't seem to go beyond 90lbs. She was naturally very thin due to a high metabolism, but she was also very athletic -- a marathon runner. We didn't fuss much with her weight until she wanted to get pregnant and her doctor thought she might have better luck if she'd gain 10 lbs. At first, my client stopped exercising and was eating tons of candy bars, cupcakes and fried foods trying to pack it on but she came back to me saying she didn't feel her best and she missed feeling high on life. She complained of bloating and fatigue and a general meh feeling. I talked her into dropping the junk food and instead eating handfuls of raw almonds and cashews (her favorites) adding flax seeds to her smoothies and adding avocado (which she loved!) to almost every meal. Within weeks she'd gained weight but within days she reported feeling fabulous, more alert and much healthier. She ended up having a baby and was a healthy, glowing mama her entire pregnancy -- she's still a healthy, glowing mama and she's still eating lots of nuts and avocados to keep the weight on.