What is your concern? Is he bloated? I can't really tell anything from the pic but am not as experienced with bettas as others on here
This is a list of questions from the emergency section, depending on what's going on it may be good to answer them.
1. Water parameters. (ammonia, nitrate, nitrite, PH, temp', Hardness etc) 2. A full description of the fishes symptoms. 3. How often you do water changes and how much. 4. Any chemicals and treatments you add to the water. 5. What tank mates are in the tank. 6. Tank size. 7. Finally Have you recently added any new fish?
You could try moisten his food with a bit of garlic juice. It may entice him to eat some. Garlic is also an immune-booster, so it would be good for his health too.