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?

A friend of mine bought me a month's worth of yoga classes over the summer. I loved it! I've never found an exercise/fitness regimen that I actually WANTED to stick with. It helped with a lot of my long-standing physical issues (balance, back pain, stress, fatigue) and was a perfect balance of stretching and strengthening for my fitness goals. The only problem is that now that my month is over... I can't really afford to do it anymore. I've looked all around for inexpensive and conveniently located studios, but I can't find anything that's in my price range or fits in my schedule. What resources are there for broke aspiring yogis? Are there any guidelines for practicing yoga at home? Are there any exercise routines that are similar to yoga (i.e., low impact, stretching + strengthening) that are less expensive or easier to do without an instructor?

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.

I know there are video games out there now that require you to move more, unlike traditional video games. Are these games, like Wii Fit, a good way to be more active or are they doing more harm than good?

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?

I have been a lacto-ovo vegetarian for three years now. I want to stop and get back to eating meat. I do not know the proper way of doing this, so I would love feedback on how to plan my meals.

I eat lots of different kinds of lentils but don't know much about their individual nutritional properties. Are certain kinds of lentils healthier than others? What are the different calorie and protein figures for different kinds of lentils?

Is milk good or bad for you?