Fasting: Pros and Cons for Weight Loss

Proponents of intermittent fasting contend that this popular way to lose weight is better than conventional dieting. But this type of diet isn’t necessarily best for everyone, a top expert says.

“Fasting is currently one of the newest diet fads and, while there are studies showing benefits, there are also potential downsides,” Dr. Kent Holtorf tells Newsmax Health.

A recent University of Illinois at Chicago study finds intermittent, or alternate-day fasting, was equal in results to calorie counting when it came to weight loss, along with keeping off the excess pounds.

The study, which followed 100 obese people for a year, found that those who engaged in intermittent fasting lost 6 percent of their body weight, while those who ate a calorie-restricted diet lost 5.3 percent, not a statistically significant difference, the researchers say in JAMA Internal Medicine.

Holtorf is the Los Angeles-based medical director of the Holtorf Medical Group and a founder and director of the nonprofit National Academy of Hypothyroidism. He also has appeared as a medical expert on several TV shows, including “The Today Show,” “Good Morning America,” and “ABC News.”

Here are excerpts from his recent interview with Newsmax Health.

Q: What exactly is intermittent fasting?

A: The idea is to intermittently significantly reduce calories in a strategic way to reduce overall caloric intake instead of eating less per day. One common method is called the 5:2 diet, which involves significant caloric restriction two non-consecutive days per week while eating normally the other five days.

Q: How did this type of diet catch on?

A:  Several studies were published showing that severe periodic calorie reduction had been shown to have many benefits including changing gene expression and stimulating cell repair, reducing the risk of Type 2 diabetes, improving cholesterol, lowering the risk of cholesterol levels, reducing heart disease and cancer risk and even extending lifespan.

Q: What do you think of intermittent fasting for weight loss?

A: There is a large amount of research supporting the safety and efficacy of intermittent fasting. If an individual fasts for a designated period of time, weight loss is to be expected as caloric intake has been reduced; however, research finds fasting offers long-term benefits including reduction of inflammation and improvement in mood. For example, a randomized, clinical trial of 71 people who followed intermittent fasting for three months lost an average of 5.7 pounds while the weight of the control group, which didn’t alter their eating habits, lost no weight. Those in the fasting group saw a reduction in blood pressure, body fat, and waist size.

Q: What effect does intermittent fasting have on mood?

A: Going without food for 10-16 hours causes the body to release fatty acids known as ketones. According to Mark Mattson, a senior investigator for the National Institute of Aging, who has done extensive investigation on the health benefits of intermittent fasting, ketones have been shown to protect memory and learning function as well as slow disease processes in the brain. Ketones are also shown to boost the body’s formation of particular stress reducing neurotransmitters, such as serotonin and GABA, which helps you stay calm under stress and have fewer cravings.

Q: What are the drawbacks of using this type of diet for weight loss?

A: While it can be a way to jumpstart weight loss and have health benefits, studies also show that it can permanently reduce metabolism (calories burned per day). The metabolism may not go back to normal when normal eating is resumed unless steps are taken to prevent or reverse the drop in metabolism. Thus, fasting or so-called “yo-yo dieting” can contribute to long-term weight gain, wiping out the short-term health benefits of fasting.

Q: Are there any groups for which this may be a particular problem?

A: This is shown to be more of an issue for women because women’s bodies appear to perceive fasting as more of a threat of starvation and respond by lowering metabolism to survive the perceived famine. This is especially true if a woman has any signs of low thyroid, including low body temperature, depression, cold intolerance, PMS, cold extremities or suffers with fatigue.

Q: So is there any one best diet out there for everyone?

A:  Studies show that most diets are successful short-term but most suffer from equal long-term failure. But thyroid evaluation and optimization, if low, can increase the likelihood of successful weight loss whether via fasting or other diet plan.