Does it cost you money being overweight? I think it does. Many would argue that it depends on what you define as overweight, but I think that if you feel "overweight" you likely are.
What sort of costs are involved with being overweight? Well for many people it can cause increased medical costs. Such as taking medication to control high blood pressure, cholesterol, or diabetes. I read in NEJM that 1 pound of extra weight = 4 extra pounds on your knees, so overweight people are also likely overstraining their joints and bones, possible also causing them to take painkillers. Even with prescription coverage, these medications can add up if you have to continually pay the co-pay every month.
Second, it's harder to find clothes. I have talked to overweight people who find it difficult to buy clothes. Sometimes the clothes need to be altered. Or they need to shop in speciality stores and pay more. Thus they are usually unable to shop sales or thrift stores.
Third the grocery budget. Being overweight typically is due to eating more calories than you expend. To lose one pound you need to expend 3500 more calories than you ate. So imagine being 10 lbs overweight means you potentially ate an extra 35,000 calories. That's a lot of food. People have distorted what a proper portion size is. So people often eat more than the suggested or reccomended serving.
All these things do add up. If you wanted to save money, and you've already cut your budget, consider looking at your health. If you are overweight, maybe you can lose weight and decrease your medical and grocery budget. The benefits will be more than just financial.