Limit portion sizes to 200 calories. You can buy as much as you want. Get that out right away. This would be limited to prepared foods. Restaurants only, really. You would be allowed to order whatever you want, and in the quantities you want to, but you would know full well that each portion is 200 calories. I'm using an economic theory applied to nutrition. In order for consumers to make the best choices, they need to be properly informed. With the best information, they will make the best choices. Restaraunts, mostly fast food, do their best to obfuscate the nutritional information on their products. So, add a leveling factor. Make it so no matter what you order, no matter where you order it, it will be 200 calories. Then let the market decide what it will consume.