Here's the BMI (Body Mass Index) chart from the US National Institute for Health:

At 74 inches height, I should be a minimum of 148 pounds to be 'healthy'. I typically run 140 +/- 3 pounds, and have held that for over 30 years (8 pounds below 'normal'). I'm not bulimic, but I *am* concerned enough about my health and weight to have changed my eating habits to maintain my preferred average BMI. Back in the late '70s I started eating less and less each week until I found out what amount of food I needed to keep my weight at the
happy mark, and I've stayed there ever since.
When I was in college, I noticed that I was getting a bit of fat around my middle which I found unappealing, so I asked the campus doctor, "How do I eat to be healthy?" He was surprised and pleased, and said "Good question!" He replied that you should eat enough every day to have a bowel movement about the same size and consistency of a single large banana, and if you're eating the proper mix of foods it should float.
I've continued to casually research eating and health since then, and found out that Europeans and Americans eat roughly 4 times as much meat as is recommended for optimal health, so I cut out meat except for once or twice a week.
At 53 years old, I'm still the same shape that I was back in college, sans the little bit of fat that I had initially. I rarely get sick, compared to everyone around me, and the only issues I've had since college was the onset of arthritis in my late '30s (it's in both sides of my family). Six years ago I added a tablespoon of flax oil plus two heaping tablespoons of cottage cheese to my diet every day and the arthritis
disappeared, so today I have *zero* medical issues aside from anemia, and I take a daily iron supplement to correct that.
Compared to virtually EVERYONE my age in Texas, I'm in excellent shape. I have more vitality & energy than most people half my age, and I'm happy with myself. Is that 'sexy'? Well, 13 young women in Mexico thought so!

People learn to eat from their parents, and if your parents don't eat correctly, you won't either. You can CHOOSE to eat differently if you make the lifelong commitment, though. It's not a
diet, it's merely
eating right.