I am very interested in nutrition and enjoy eating a well-balanced diet because it makes me feel healthier, happier and more energized. I also have a terrible sweet tooth, which I combat by simply not buying junk food when I shop for groceries (although I will indulge on rare occasions). This strategy has worked for me very well — up until now.

I am living with my boyfriend who, despite even his doctor's warnings, has a rather unhealthy diet. In an effort to nudge him in a better direction, I have offered to cook most of our meals at home myself, but with little success. He's a picky eater and often declines the meals I prepare in favor of pizza or Chinese take-out instead. I would just give up and let him clog his arteries, but his unhealthy habits are starting to affect me. When he brings home tacos, or especially bags of candy, I inevitably eat them also. I am a decent cook, but a greasy pizza always tastes better. If I can't change his habits, how do I at least keep him from changing mine?

Here's a food preparation question: I made a large tomato sauce with meatballs and several pork chops in it. I cooked it for two hours and turned the heat off at 1:00 AM and went to bed without putting it in the refrigerator. I awoke at 8:00 AM and the sauce was a few degrees above room temperature. If I reheat the sauce, will it be all right to eat? Thanks.

For as long as I can remember, I've been using my back muscles when I did sit-ups. In fact, I distinctly remember the first time we did them in second grade. After a few reps, it was already so painful that I was having trouble breathing properly. Being eight years old, however, I didn't realize this was a warning sign and assumed it was normal.

Flash forward ten years, and I have almost no strength in my abdominal muscles. I've tried to teach myself to do curl-ups properly, but no matter how hard I try, I can't even lift my head without using my back muscles. Exercise balls are no help either. Even when I concentrate on using my abs to keep myself steady, my back is still doing 95% of the work.

So, in short, I have two questions: Am I at risk for having damaged my back from years of abuse, and how can I work on strength training my abs now?

1) Which foods, if any, have negative calories?

2) I have recently started a weight loss plan and after doing some research I learned about calorie burning foods. My question is, are there really calorie burning foods or is it just another diet fad?