I'm not sure how I feel about this question.
I've often been troubled by the idea that seems popular that excess weight *causes* health issues like heart disease, high blood pressure, etc. It seems more likely to me that the behaviours that cause excess weight cause the heart disease & other issues. It's a small distinction, but an important one because it means that theoretically, if one was as Jessica suggested, one could have extra weight due to overeating healthy foods and still be healthy.
There's the question of degree too though, as others have suggested. 15-20 lbs overweight is one thing, 100+ is different. Being obese would put strain on your heart muscles, knees, respitory system, everything. I can see that it would be hard to be considered healthy & be obese.
At 170 lbs, I'm technically overweight, but my blood profiles are excellent, I run 3-4 times a week, weight train, don't smoke, I'm not a workaholic, I eat healthily and sleep well. Do I think the 11 lbs I'm overweight according to the BMI index necessarily means I'm less healthy than my junk food eating, smoking, never exercises, works too hard sister who happens to fall within a normal weight BMI? No. You can't convince me that by virtue of those 11 lbs only, I'm less healthy than she is.