My suggestion to you is to take your food with you. I don't know what all the scrawny to brawny program requires, but I'd imagine lots of protein, veggies, etc. Beefy jerky to good to take with you all the time. You can make protein shakes using a shaker bottle, Grow! in a baggie, and a decent drinking fountain. Not too many veggies go bad if you leave them out for a reasonable amount of type.
If you really need to have some refrigeration, I suggest getting one of those cooler bags. Not a hard cooler, but is light weight cloth with a plastic insulated lining. You can use freez paks or zip lock bags full of ice cubes to keep it cool. Then you can take dairy, eggs, etc. One of these bags probably is in the ballpark of $15 - $20. The one I use for work everyday has last for the last 3 years and well worth the investment.