A healthy meal will not give you three hours of energy. Instead, eat healthy meals throughout the day. When hungry, eat again.
Many people try out a healthy diet but don’t eat enough food. A big salad has much fewer calories than a big plate of pasta. The salad and pasta plate take up the same space, but the salad is all water and lots of air between the leafy greens.
Cooked food, aside from a stew, looses its water. This makes it dense without water. Fruit may be dense, but it’s mostly water. Eating fruit is almost like drinking water. How long after drinking a glass of water would you get hungry again? Quickly.
There are some dense fruits such as dates, figs, and avocados. I add dates and peanut butter to my banana smoothies to get more calories.
Regardless, one must always eat more food when eating healthy food.