Most people imagine David was a mighty warrior and very strong. However, he was weak and very thin from fasting. He probably fasted often.
Here is the key Bible verse:
Psalm 109:24. My knees are weak through fasting. My body is thin and lacks fat.
My knees are weak. When you fast, you will soon feel weak.
My body is thin and lacks fat. David could have any food as he wanted. He could have as much of it as he wanted. But he was thin and lacked fat. He probably fasted quite often.
Fasting is only for those who are medically capable. Check with your health care provider. Experts say you need to be under the supervision of a doctor during the time of a fast.
Unless otherwise noted, all Bible quotations on this page are from the World English Bible and the World Messianic Edition. These translations have no copyright restrictions. They are in the Public Domain.