It could possibly be due to citrin deficiency.

It is possible that you are not eating enough food, or that you are using more energy due to changes in your lifestyle. These could also be symptoms of hypoglycemia. Regardless, you need to eat now to supply energy to your body. When you feel like you want to snack on something with higher carbohydrate content, start with a smaller portion, and consume it alongside other food/beverages such as milk, cheese, yogurt, or meat/fish. MCT can also be a good supplement for your energy need.

You may want to revisit your recent diet and make sure that you take enough nutrients and energy with your three meals and snacks and take note to eat more food when your activity level is higher. Rest more when you feel tired.

If you continue to feel unwell or if your appetite does not return, please consult a doctor as it could be something other than citrin deficiency that is causing these issues.