Yep, and when I'm outside in the middle of the day(in other words, the HEAT is a big factor in that, too) for an hour, it makes thing worse. I know it's making me healthier, physically, but at the same time, I would like to maintain my weight, and not lose so much that I lose my figure (hey, I'm a girl. what do you expect?).
I've thought about carrying a bottle of Gatorade with me when I'm outside in the heat (it's supposed to get worse in the summer, with all the concrete).
I assume you're talking about last year. It cannot possibly be that hot outside right now.
As for the advice, get a physical (to rule out existing problems) and follow a common sense plan. Drink plenty of fluids, stay away from soft drinks and take multivitamins. The phosphorus in soft drinks will take nutrients away from your body (like calcium). I wouldn't do any type of "diet". Follow something that suggests lean protein, whole grains, fruits, veggies, fiber, etc...nothing that's a fad or requires you to do strange things. And a protein bar is good while you're outside and can't sit down to a meal. Just don't make them a centerpiece of your diet.
And ignore BMI charts. They do not take into account muscle mass. Your ideal weight is a bit more complex than going by your weight and height. As long as you're healthy and your organs are functioning properly, what the scale says shouldn't matter. Our nutritional needs change as we age, especially with women because of our hormones. Go see a nutritionist if you don't get satisfactory answers from the clinic.
