If you find yourself sharp and productive one moment, then foggy, distracted, or exhausted later, your blood sugar may be part of the picture.What doesn't help is assuming every afternoon slump means you need more coffee.

If your joints feel stiffer than they used to, you may think the answer is simply resting more. What doesn't help is avoiding movement altogether.

If you're constantly tired, it can be frustrating not knowing why. What doesn't help is assuming every kind of fatigue has the same solution.

If you're tired, struggling with your weight, or feeling unusually sluggish, you may wonder whether your thyroid is involved. What doesn't help is jumping into restrictive diets, "thyroid detoxes," or expensive supplements.

If you're over 50 and focused mainly on cardio, walking, or weight loss, there's one thing you shouldn't overlook: muscle.