While one meal a day may be okay for people who are already healthy, it is a big mistake for people who are sensitive to levels of blood sugar such as diabetics and pre-diabetics. Blood sugar has a direct connection with mood, ability to concentrate and hunger. The absorption rates of carbohydrates can be somewhat control by eating low glycemic carbs. Blood sugar levels are affected throughout the day by food, exercise, stress and must be controlled through regulation of food, even for those who use medication and insulin. Diabetics simply cannot eat one meal per day and expect to stay healthy.
So the "one meal a day" thing must be considered in light of one's own health. If you are sensitive to changing levels of blood sugar, lack of appropriate amounts of carbs at specific times will only result in problems. And all the meditation you can do will not save your eyes, kidneys or legs.