Dear Dietitian: IF

Leanne McCrate
A sample IF schedule.

Dear Dietitian,

A close friend of mine has recently lost thirty pounds on an intermittent fasting diet. It reminds me of crash diets that were once popular. Is intermittent fasting a good way to lose weight?



Dear Judy,

Intermittent fasting (IF) is the one of the latest fads in weight loss. This is a type of weight-loss plan where one eats during certain times, then fasts for so many hours. There are always diets that claim to have the magical formula for weight loss, so I set out to find if intermittent fasting has any advantages over moderate calorie restriction.

This plan of eating focuses on the times you eat rather than what you eat, but most do not recommend going “hog wild” during the eating times. There are different types of IF: one is 5:2, where you eat normally during certain times for five days, then fast for two days. On fasting days, calories are limited to 500-600 per day. Other forms include fasting every day for 12 – 16 hours. The premise of this diet is that when our bodies go into a fasting state, it allows us to use energy stored in our fat cells, thereby breaking down fat and resulting in weight loss.

There are some things to consider before starting an intermittent fasting plan. Some people have difficulty on the fasting days. They may get headaches from decreased blood sugar levels, feel irritable or tired.

In a randomized study of 100 participants, Trepanowsky et al. found that IF did not produce more weight loss than overall calorie reduction. This study was published in the Journal of the American Medical Association. Other studies have found that IF improves insulin sensitivity and may help prevent diabetes.

In summary, if intermittent fasting is a practical plan for you, then go for it. Remember the basics: a diet high in fruits and vegetables, and choose whole grains and lean proteins.

Note: If you currently have insulin-dependent diabetes, do not try intermittent fasting. It may result in dangerously low blood sugar levels. Talk to your doctor before starting a weight-loss plan.


Dear Dietitian

Leanne McCrate, RD, LD, CNSC is a Registered Dietitian, Licensed Dietitian, and Certified Nutrition

Support Clinician from St. Louis, Mo.