Interacting problems of weight gain and sleep apnea make it difficult to help yourself off the slippery slope of health problems.
Food is also related to sleep by appetite and metabolism. People who don't get enough sleep are more likely to have bigger appetites due to the fact that their leptin levels (leptin is an appetite regulating hormone) fall, promoting appetite increase.
As you gain weight your sleep apnea will get worse for a variety of reasons. Your blood pressure is usually high if you are overweight, well having sleep apnea spells with increase that already high blood pressure. This can cause a stroke or even death
Even losing 15 or 20 lbs can mean a big change for some people. Work with a dietitian to create a balanced diet you can live with. Ask your doctor for an exercise program.