Reflecting on the fact that there are starving people in the world is to help us feel fortunate that we have food to eat, in order to make us more content.
Fine, we become more content, but then what are you going to do with that? That's how you alleviate the guilt. If you just simply use the food reflection to be content, "Oh, yeah, I have a lot of food, I even have yummy food. Oh I like it, I like it!" If you use the food reflection just to be more content, more happy in the moment, then you are wasting an opportunity.
The fact is: you have a wonderful opportunity with your life. What are you going to do with it? There are many people on this planet who have a huge bank account. They go into the bank and take money out from their account whenever they want. What happens, especially in the West, is that some people have tons of money when they are born. They use it, they use it, they use it, but they do not put more money into the bank.
Putting more money into your bank account, putting more good Kamma into your Kamma bank account is very important. Otherwise, you may not have so much food and such good food in the future. Use the food reflection to have more contentment with what you do have, knowing that you have much more than others. But remember to then use it to understand how fortunate you are right now, and that you are going to have more good fortune in the future, if you do more good Kamma. You have to make a bit of a dedication here, to keep doing good things. Then you won't have the guilt that you are eating and other people aren't.