Intermittent fasting is an integral part of our history. Our early ancestors managed without three meals a day, and fasting has long been observed in many cultures and religions, including Judaism, Hinduism, Buddhism, Islam, and Catholicism. Recently, fasting became a new diet trend, but the question remains: are there true health rewards for periodic breaks in eating?
The pros. Intermediate fasting can take on many forms, including significant restriction in one’s daily caloric intake, skipping a few meals during the week, or completely avoiding food for up to 24 hours during a specified period of time. Research suggests that intermediate fasting may offer health benefits, such as better cognitive health, improved glucose metabolism, and perhaps even prolonged life, according to a scientific review published in 2006. In addition, weight loss may be a main benefit. A 2010 study published in International Journal of Obesity found that among overweight women, intermittent fasting (75 percent reduction in calorie needs two consecutive days each week, followed by 100 percent of estimated calorie needs for five days) produced an average weight loss of 14 pounds over six months—two more pounds less than in women who ate an average of 1,500 calories each day.
The cons. Other studies point out that intermittent fasting may not be so promising, however. The same 2006 scientific review points out that excessive caloric restriction may lead to extreme loss of body fat and decline in sex steroids, which may cause menstrual irregularities and the development of osteoporosis in females. A 2010 study published in the Journal of Cardiac Failure found that rats subjected to intermittent fasting developed stiffened heart tissue, impairing the organ’s ability to pump blood effectively. And some research suggests that eating regularly throughout the day may be a better weight loss strategy, as it helps to reduce overall caloric intake and boost metabolism. Indeed, a randomized trial reported at the scientific meeting Obesity Week in Atlanta in 2013 found that patients who fasted every other day lost about the same amount of weight over two months as those who did not fast and ate a standard diet. Health experts also are concerned that fasting may potentially mask eating disorders and trigger unhealthy habits, such as preoccupation with food and poor body image. The practice is not advised for individuals with diabetes, as it can lead to hypoglycemia (low blood sugar.)
The bottom line. While intermittent fasting may be part of one’s cultural traditions, it may not the best or safest diet for everyone. More research is needed before we fully understand the body’s response to fasting and whether it provides real benefits. For many people, it’s best to eat balanced meals and snacks throughout the day, providing a consistent supply of important nutrients that prevents blood sugar lows and their associated symptoms, such as mood swings, headaches, clouded thoughts, hunger, and fatigue.
— McKenzie Hall, RD