March is National Nutrition Month. Throughout the month, Harris Health dietitians provide in-depth analyses of popular diets many Americans are following in hopes of losing weight and improving their health.
Typically, dietitians encourage their patients to focus on portion control and self-discipline in lieu of dieting. This ongoing series will give readers an opportunity to learn about the benefits and shortcomings of popular diets. Today, we take a closer look at intermittent fasting.
Parvin Rafiee, MS, RDN, LD, clinical dietitian, Baytown and Settegast health centers, is fascinated with the effects that food and dietary habits can have on the body. In the article below, she explores intermittent fasting—a popular new pattern of eating and fasting.
Intermittent fasting describes a period of eating followed by a period of fasting. This pattern can
be practiced three different ways:
1.) time-restricted feeding: 4-8 hours of eating, 16-20 hours for fasting, repeated daily
2.) whole-day fasting: 5-6 days of eating, 1-2 nonconsecutive days of fasting
3.) alternate-day fasting: 1 day of regular eating, 1 day of fasting, repeated
The main benefit of intermittent is losing body fat, which translates to weight loss. Glucose and glycogen are short-term sources of energy for the body. When short-term energy is depleted, the body uses its long-term energy stored in body fat. In another words, the body will not burn fat while glucose is available. When we eat throughout the day, our insulin level stays high and our body can’t utilize fat for energy; during fasting, our insulin level falls, which enables body to access other food stores (fat) for energy.
Calorie restriction typically results in 75 percent fat loss and 25 percent muscle mass loss. However, intermittent fasting helps maintain muscle mass. In this lifestyle choice, the ratio is different—90 percent of weight loss is fat and 10 percent is muscle. Experts state alternate daily fasting over 70 days reduced body weight by six percent, and fat mass decreased by 11.4 percent. Breakdown of muscle tissue occurs at low levels of body fat (approximately four percent).
At this level, there is no more body fat to be used for energy so muscle will be broken down for energy. Overweight or obese patients should not be concerned with the muscle loss since body fat percentage is higher than four percent. Maintaining muscle with intermittent fasting helps to sustain higher metabolism compared to traditional calorie restriction.
During time-restricted intermittent fasting, you’re consuming zero calories for 16-20 hours. On whole-day fasting and alternate-day fasting, you can consume 500 calories per fast day to stimulate fat loss but preserve muscle.
Water, tea and black coffee are allowed during fast periods among all three types of intermittent fasting. During eating, you can enjoy your foods as long as you stick to healthy food options. You just need to consider that this eating pattern isn’t magical—you still need to restrict your calorie level in appropriate range for your body size to provide enough calories without overeating.
Intermittent fasting can be considered as a different approach to calorie restriction. Additionally, research has shown fasting to significantly improve LDL cholesterol and triglyceride levels. Intermittent fasting and calorie restriction enhance cardiovascular and brain functions, improve coronary artery disease risk factors, reduce blood pressure, and increase insulin sensitivity. In conclusion, intermittent fasting shows promise in improving weight management and overall health.