Too much body fat puts you at risk for chronic disease, but having too little can also endanger your health and well-being. Older adults or those recovering from illness sometimes experience unintentional weight loss that leads to very low body fat levels. If your body fat percentage is too low, your doctor may advise you to gain a modest amount of fat to improve your health.
About Body Fat Percentage
Your body is made up of fat tissue and lean tissue. Lean tissue includes muscle, bone, organs and connective tissue. Fat tissue is made up of essential fat and storage fat. Essential fat -- which exists within the marrow of bones -- forms the foundation for the central nervous system and contributes to the structure of some organs. It's necessary to have some essential fat, because the human body needs it to function properly. For good health, at least 3 percent of men’s body weight needs to be essential fat. Women have more essential fat – at least 13 percent --- because women’s hormones drive the storage of more essential fat, which supports the possibility of pregnancy and breastfeeding.
When most people think of fat, they visualize storage fat, which lies just beneath the surface of the skin and also deep in the belly around the internal organs. Some storage fat helps regulate your temperature, helps absorb vitamins and cushions internal organs. The average, healthy percentage of body fat for adults is about 15 to 20 percent for men and about 20 to 25 percent for women.
When your body fat is low -- below 8 percent for a man or 13 percent for a woman -- you might not look or feel your best. Increased body fat levels will increase your energy and improve your resilience to infection. A body with a healthy amount of body fat is more likely to have well-functioning cardiovascular, endocrine, reproductive and gastrointestinal systems. By putting on fat, you prevent the drastic complications that result from being too thin such as heart damage, infertility, muscle loss or death.
Increasing Body Fat Healthfully
To gain fat, you need to consistently eat more calories than it takes to sustain your current weight. A surplus of 250 to 1,000 calories a day will help you add 1/2 to 2 pounds a week. Focus on increasing your consumption of nutrient- and calorie-dense foods. Examples of these include whole grains, dried fruit, nuts, full-fat dairy, avocado, seeds, and starchy fruits and vegetables. Although junk foods, fast foods and sweets are calorically dense, they have exceptionally high quantities of sugar, saturated fats and refined grains, none of which promote good health.
To help add calories, eat larger servings of the healthy foods you enjoy. To increase your calorie intake further without eating large quantities, add calorie-dense "extras" to meals and snacks. Spread nut butter on toast for an additional 190 calories per 2 tablespoons, cook hot cereal or canned soup in whole milk for an additional 160 calories per cup or sprinkle 1/4 cup of sliced almonds over salad for about 135 calories.
Strategies That Boost Fat Gain
If a jam-packed schedule keeps you from eating all the calories you need, put a handful of nuts, dried fruit or granola into a baggie to snack on throughout the day. Having a homemade, high-calorie shake made with a cup of whole-milk yogurt, a small banana, 2 tablespoons peanut butter, a tablespoon of ground flax seed and 1/2 cup of whole milk will give you nearly 560 calories. Squeeze a little honey into your shake, if desired. Have the shake between meals or as a bedtime snack. If you're having difficulty eating enough, talk to your doctor about the possibility of adding store-bought nutritional shakes.
Grazing on multiple mini-meals, instead of three large meals, also helps you take in additional calories without feeling uncomfortable or stuffed. Eat meals with friends or family so you feel more inspired to eat. Dining with others may expose you to dishes that you're unlikely to prepare on your own but that you enjoy immensely, so you’ll eat more. If you're bored with the same meals or have compromised taste buds, try new spices or recipes to punch up the flavor.
Gaining Fat vs. Muscle
When you’re adding pounds for sports performance or for increased fitness, muscle is often the preferred tissue to gain. If you're at an extremely low weight and have a low body fat level, initially, you'll need to focus on gaining fat to increase your body fat percentage. To optimize fat gain, refrain from formal exercise until your doctor says it's OK. When you are sedentary and you gain weight, the fat makes up two thirds of every pound gained.
Make sure you're getting enough protein in your diet, even when your focus is to gain fat. Dietary protein supports the formation of muscle mass and is essential for keeping every tissue in your body strong and healthy. An underweight adult who's trying to gain weight needs about 0.5 to 0.7 grams of protein per pound of body weight. For example, if you weigh 120 pounds, shoot for 60 to 84 grams of protein a day. That's doable, because you can have 15 to 20 grams at each meal and 10 grams at each of 2 or 3 snacks. For reference, 3 ounces of broiled steak has about 23 grams of protein; 1/2 cup of cooked, diced chicken meat has 20 grams and 1 cup of creamed cottage cheese has 23 grams. As you gain weight and begin to exercise more, you may need to increase your daily intake of protein.
Once you're healthy enough, check with your doctor about the possibility of adding strength training to help you build more muscle mass. In the meantime, help your muscles and joints stay functional by doing some movement that's essential to daily life such as carrying groceries or sweeping the floor.