Maintaining a healthy body weight is important, but it should not be confused with physical fitness. Being thin alone does not protect you from health conditions associated with a sedentary lifestyle.

Research supports fitness.

A person can appear thin while having excess visceral fat (the fat around vital organs that increases disease risk), which makes weight by itself a poor indicator of overall health. Researchers use the term metabolically fit to describe a person who is a regular exerciser and overweight, but is without health risk factors, such as high cholesterol or high blood pressure. Studies show that, despite being overweight, the metabolically fit have no higher death risk than those who are fit and maintain a normal weight.

This research indicates that thinness doesn’t always equal fitness, but that is no reason to abandon your weight-loss goals. Maintaining a healthy weight puts less stress on your bones and joints and can improve your energy levels.

Measure your fitness.

Fitness should be your goal regardless of your body weight. There are three components that define your total fitness level:

• Cardiorespiratory endurance – Often measured by the step test. It is the ability of the heart, lungs, and vascular system to work together to transfer oxygen and carbon dioxide within the body during activity.

• Muscular endurance, power, and strength – Often measured by push-up tests, sit-up tests, and handgrip. It is the ability of the muscles to contract, generate force, and sustain repeated contraction.

• Flexibility – Often measured by the sit-and-reach test. Flexibility is a measure of the range of motion around joints.

Fitness centers, worksite health fairs, and university exercise labs provide tests for these components.

Pass these health tests.

Health tests help you identify risk factors for heart disease, diabetes, and some cancers. Remember that those considered metabolically fit do not have health risk factors, despite being overweight according to their BMI. Regularly schedule appointments with your healthcare provider to assess these health indicators. He or she may recommend additional tests to assess your overall health.

• Fasting blood glucose - 70 to 100 mg/dL is normal
• Triglycerides - below 150 mg/dL is desirable
• HDL cholesterol - greater than 60 mg/dL is desirable
• Blood pressure - 120 mmHg over 80 mmHg is considered normal

Exercise regardless of your weight.

Exercise is a key factor in maintaining metabolic fitness. The American College of Sports Medicine recommends that adults engage in at least 150 minutes of moderate-intensity exercise each week to improve health. In addition to cardio workouts, incorporate two or three days of strength training and two or three days of flexibility training each week for a balanced exercise program to improve your metabolic fitness.

Lori Rice, M.S., is a nutritional scientist and author with a passion for healthy cooking, exercise physiology, and food photography.