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Is my body fat too low?

Written by Heather Nakamura, MPE, MS, RD.

Personal Profile: Paul Ricci. Paul is an avid runner who became a vegetarian almost two years ago.  He lost about 15 pounds during the four months following the change in his diet, and has maintained that weight since then.  He feels comfortable at his current weight, but recently had his body fat tested at 3.7%.  He contacted me to ask if he should be concerned about his body fat being too low.  He also noted that he would like to gain some upper body strength without adding too much additional muscle bulk.

Male. Age: 41. Height: 5’8”. Weight: 146. Goal Weight: 146. 

Occupation: electrical supply sales.

Weekly Training Program: Running: 35-40 miles per week; Sit-ups and push-ups: 3-4 days per week          

Two-Day Food Diary

DAY 1:            Breakfast:        1 Bagel + 1 T peanut butter, 1 cup Grape-Nut O’s, 12 oz orange juice, cup coffee

AM Snack:      1/2 pear, 1 apple, 8 oz soy milk + coffee

Lunch:               1 Bagel, 1-cup brown rice, tofu, and veggie salad

Aft Snack:       1 banana, 1 carrot, 1 cup coffee          

Dinner:            Tuna salad sandwich, steamed broccoli, blue cheese, green salad + 2 T Oil and vinegar dressing

Day 2:

Breakfast:          2 cups bran and Corn Chex, 12 oz orange juice, coffee + 4 oz soy milk
AM Snack:        1 apple, coffee + 4 oz soymilk
Lunch:   Green Salad, banana, Coffee + 4 oz soymilk
Aft Snack:       1.5 oz pretzels, 3 mini Butterfinger bars

Dinner:            1 Boca hot dog + 2 cups pinto beans with rice, onions and peppers; salad + 2 T oil and vinegar dressing; 3 T applesauce

PM Snack:      1.5 cups bran cereal + 1 cup soy milk, small garden salad + 3 T Italian Dressing, 1 slice cinnamon bread, 1 cup Dryer’s vanilla ice cream


Diet Analysis Summary






Calories/day (for maintenance)



Protein  (g/day)



Carbohydrate (g/day)



Fat (g/day)



Saturated fat (g/day)



% Calories from Carbohydrate



% Calories from Protein



% Calories from Fat




Vitamin C – 500 mg; Lecithin – 1 T






The analysis of Paul’s two-day food diary showed that his total calories were only 85% and his intake of carbohydrate only 90% of that required to maintain his weight and support his training needs.  The macronutrient balance of Paul’s diet was a bit off, with the percentage of calories coming from carbohydrate too low and those from fat too high.  His intake of vitamins and minerals was good, however, due to the variety of foods he consumed.  The only nutrient that came up short was calcium.


1.     You did a great job of consuming a variety of fruits, vegetables and whole grains.  This was the reason that your intake of fiber and most vitamins and minerals was so good!  People often lose weight when they switch to a high-fiber diet, since fiber makes you feel fuller sooner.  In your case, however, eating high-fiber carbohydrates may make it difficult for you to always get enough to fuel your active lifestyle.  To meet your carbohydrate needs, make sure to include about 4 servings of starchy-foods at each meal (breakfast, lunch and dinner).  Four servings of starchy foods would be equal to:

·      Bread products: 4 slices of bread, 2 English muffins, a 6’ roll, or a large bagel

·      1-1/2 cups pasta, 1 1/3 cups rice, or 1 cup potatoes

·      Cereal: 1 cup Grape nuts, 2 cups cooked cereal, 3 cups flake cereal

If you don’t get enough carbohydrate at breakfast, lunch and dinner, eating a small bowl of cereal before you go to bed is a great way to top of your carbohydrate stores!

2.     Your intake of calcium was only about 50% of your recommended needs, but that is an easy problem to remedy.  Just make sure that the soymilk you drink is fortified with extra calcium.  Both White Wave and Pacific foods make calcium-fortified soymilk products, and each cup has as much calcium as regular milk.  You didn’t indicate that you put milk on your cereal in the morning, but that would be another great way to get an additional serving of calcium-rich foods in your diet.   Aim for 2-3 cups of fortified soymilk each day, or substitute one cup of calcium-fortified orange juice, which also contains as much calcium as a cup of milk.

3.     It sounds like they may have used a Futrex machine to test your body fat.  This device uses near infrared technology to measure body fat, based on how your tissue absorbs or reflects light.  The Futrex measures body composition only at one site, the bicep, which may not accurately predict total body fat.  In addition, many indirect body fat testing measures produce more error at the extreme ends of the testing range (i.e. with very lean or very obese individuals).  If you want a more accurate measure of your current level of body fat, you should have a hydrostatic weighing test performed at a local sports medicine clinic. 

I would guess that your percent body fat is not that low, but it would be helpful to have a more accurate test performed.  When an athlete’s body fat drops too low, it can increase risk for injury and lead to problems with recovery and impaired immune function.  Everyone has an optimal level of body fat when it comes to performance, and lower is not always better.  If you have your body fat retested and it truly is that low, you could benefit from increasing your body fat to a healthier level.

4.     Using body weight to build strength will work until your muscles become too strong for that resistance to be a challenge.  If you want to continue to increase upper body strength at that point, you will need to increase the resistance placed on your muscles.  If you have access to a gym or a set of free weights, start doing upper body strength exercises that result in muscular fatigue somewhere between 10 and 15 repetitions.  That should include the following exercises: chest or bench press, upper back rows, lat pulldown, bicep curls and tricep extensions.  As a runner, you could also benefit from including a balanced program of lower body resistance training.  If you don’t want to increase lean mass too much, just keep the repetitions high and perform one to two sets of each exercise.