I live in North Dakota and decided that instead of fighting the weather this winter I'd just run maintenance miles while adding swimming and stationary biking. At the same time, I adjusted my diet eliminating soda and cutting back portions. In three weeks, I've gone from 167 lb. to 156. At 6' tall, BMI calculators consider 137 to 175 healthy. I've got small bones, and am not too muscular. How do you tell when you've reached an optimum weight? I'm worried I've started a weight yoyo, although I do feel faster, and leaner. For now, I'm going to target 150 and try to hold steady.