In a study on overweight men, researchers compared exercise before vs after a meal to see how it affects fat storage and metabolism. They found that walking after breakfast led to a less negative fat balance, meaning less fat was stored.
One interesting NIH report found that walking immediately after a meal, rather than waiting an hour, was more effective for weight loss. Over a month, subjects lost nearly 1.5–3 kg walking just after lunch and dinner compared to delayed walking.
This suggests that the metabolic benefit is not just from calories burned, but also from how and when the body processes the meal.