Effective Dietary Practices of Active People with Diabetes:
Part 4 (Importance of Protein and Fat)
By Sheri Colberg, Ph.D., FACSM
Fat: Used Some But Not as Much as Carbohydrate
Both the fat stored in your muscles (i.e., intramuscular triglycerides) and circulating around in your blood (free fatty acids) can provide some energy for muscle contractions. Although carbohydrate is the main energy source during exercise, fat is an important contributor to your fuel needs, particularly during low-intensity or slower, prolonged activities like walking the dog or taking an all-day hike. Fatty acids are stored in your adipose (fat) tissue as triglycerides and are released by hormones (mainly epinephrine) to circulate around to the active muscles. Not much of the intramuscular fat is used during activities — unless they are extremely prolonged, lasting many hours at moderate intensity — but later when you’re resting they kick in some of the energy for recovery, which is largely fueled by fat from all sources. Fat is hardly used at all during high-intensity aerobic and anaerobic exercise, both of which rely on carbohydrate for ATP production. Fat contributes most during prolonged low-intensity activities, and it provides most of the fuel for recovery from any physical activity.
Your blood sugar may stay more stable overnight if you eat a higher-fat bedtime snack, such as ice cream, yogurt, or soymilk, on days when you’ve been particularly active. Fat is metabolized much more slowly than carbohydrate and will provide an alternative energy source for your muscles five to six hours after you eat it. Eating high-fat foods for exercise (a practice called fat loading) may be detrimental to your performance, however, and it is not advised. Also, keep in mind that any fat that you eat before and during exercise isn’t digested and ready for use for many hours, and the fat consumed may slow the absorption of any carbohydrate that you eat.
The current dietary guidelines recommend a fat intake of 20 to 35 percent of daily calories. Many diabetic exercisers may consume more than 35 percent as fat, which is fine as long as they take into account the type of fat. You should aim to minimize your intake of saturated fats (mostly solid at room temperature, found in cheese, margarine, meats, and more), trans fatty acids (bad partially hydrogenated fats added to foods by manufacturers, now listed on food labels), tropical oils (coconut, palm, and palm kernel oils), and interesterified fats (the new trans fat substitute added by food manufacturers). All these fats can raise the levels of the bad type of cholesterol (LDL) in your blood and raise your risk for heart disease and stroke. If you choose to have a moderate fat intake after prolonged exercise to prevent later-onset lows, pick better fats like those found in nuts, peanut butter, olive oil, fish, flaxseed, and dark chocolate, or at least choose lower-fat varieties of dairy and other foods (e.g., fat-reduced ice cream, yogurt, and cheese).
Protein: Important for Recovery and Muscle Repair
During most exercise, protein contributes less than 5 percent of the total energy, although it may rise to 10 to 15 percent during a prolonged event such as a marathon or Ironman triathlon. Regardless, protein is never a key energy source for exercise, but it is critical for other reasons. Taking in enough protein in your diet allows your muscles to be repaired following strenuous exercise and promotes the synthesis of hormones, enzymes, and other body tissues formed from amino acids, the building blocks of protein. About half of the 20 amino acids are considered essential in your diet, meaning that you have to consume them or your body will suffer from protein malnutrition, which causes the breakdown of muscles and organs over time. Your body can make the rest of the amino acids by itself, but you need to have enough of all of them–essential and nonessential–to synthesize protein during recovery from exercise, which is a vital process if you want to experience any increase in the strength, aerobic capacity, or size of your muscles.
The current recommended intake of protein is 10 to 35 percent of total daily calories. Athletes who train regularly likely should consume somewhere in that range, as long as they are minimally consuming at least 1.2 to 1.8 grams of protein per kilogram of body weight (e.g., 84 to 126 grams of protein for a 70-kilogram exerciser). Typically, an ounce (28 grams) of chicken, cheese, or meat contains about 7 grams of protein. Taking in more protein and slightly less carbohydrate postexercise may also help keep blood sugars stable after exercise and facilitate the uptake of both into your muscles.
Because protein is not a major energy source during exercise, you really don’t need to worry about consuming any right before or during an activity. Research has shown, however, that taking in some protein along with carbohydrate right after hard or long workouts may help your body replenish its stores of muscle and liver glycogen more effectively. Although the benefits of postexercise protein have not been studied in diabetic athletes, taking in a small amount of protein along with your carbohydrate (in a ratio of 1:4) after an activity may help prevent low blood sugars later. A 2009 study also showed that chocolate milk is superior as a recovery drink for nondiabetic athletes compared to sports drinks. Protein takes three to four hours to metabolize after you eat it — more time than carbohydrate but less than fat — and a small portion of it is converted into glucose, which can raise (or prevent drops in) your blood sugars when it finally does show up in your bloodstream. For that reason, you may also want to have some in your bedtime snack (along with fat and carbohydrate) when you’re trying to prevent nighttime lows after a day of strenuous or prolonged activity.
This column is excerpted from Diabetic Athlete’s Handbook
(released November 2008 from Human Kinetics), which contains essential exercise-related information and examples for Type 1, Type 1.5 and Type 2 diabetic exercisers. More information is available at www.shericolberg.com.