A scenario most of us have thought about, exercising after eating a meal. Is it one of those things that depends on how much you eat? Or is the real question whether there's a do or don't to getting straight up.
The simple answer is that if you've eaten a lot, then exercising after eating a meal isn't a good idea - when you eat, a significant amount of blood is diverted to the stomach and intestines to help digestion. This means that less blood is available for muscles, and as a result, you may experience cramping. While there's no simple answer to how long you should wait, most people find they need to wait between one to two hours before any strenuous workout.
However, there will often be times when you need to eat just before a workout. In that case, it's important to think about what you eat. If you have a light, high-carbohydrate snack - some low-fat pretzels, an apple or banana - you should be able to workout almost immediately. Other alternatives are energy bars, protein shakes, or a pot of yoghurt. Indeed, experience from triathletes in ultra-distance races shows that you can probably eat most of these types of foods in the middle of a workout.
Other factors to consider are the nature of the workout. Going for a brisk walk shortly after eating is much more feasible than taking a strenuous high impact class or engaging in a heavy weights session. The bottom line is that this is an area where experimentation is required. By trying a variety of foods, and different intervals between the time you eat and when you start your workout, will enable you to figure out a food/workout timetable that works for you.