Intermittent Fasting – Just Another Fad or Lasting Trend?

Intermittent Fasting is a diet strategy with varying periods of fasting combined with normal calorie intake.  Depending on the method of fasting you use, intermittent fasting may not necessarily mean you are restricting calories.  Intermittent fasting has increased in popularity due to the reported health benefits such as improvement in metabolic abnormalities (i.e. insulin sensitivity, blood glucose, triglyceride and cholesterol levels) and weight loss.  If you are wondering whether intermittent fasting is for you, here is the lowdown on strategies and the possible benefits and disadvantages of this diet.

Extended Overnight Fast. The most common method of intermittent fasting is the time-restricted feeding, which utilizes the overnight fasting period when you are sleeping.  This is a time-restricted fast, not a calorie restriction diet. Most people aim for a 16-hour fast by either eating an early dinner or a very late breakfast.  This decreases the duration of time when you eat to 8-hours each day.

Pros

This fast is relatively easy to incorporate into your lifestyle and does not require a lot of planning.  Some studies resulted in weight loss and lower blood sugar and improved cholesterol levels.

Cons

There are very few studies on the time-restricted fast in humans so the health benefits of this method of fasting is not clear.  You are likely to feel very hungry in the morning before breaking the fast.

Alternate-Day Fast. This method involves a complete fast on days when no food or calorie containing beverages are consumed alternating with your usual diet.  Unlike the time-restricted fast, this method results in an overall calorie reduction for the week.

Pros

Some studies show improvements in blood glucose or insulin sensitivity, cholesterol levels and a modest weight loss.

Cons

This may be very difficult to fit into your social life and requires a lot of planning. You may experience extreme hunger on the fasting days or other more serious health consequences. Speak with your doctor first.

Two-Day Fast (5:2).  This is considered a modified fast where calories are reduced to about 20%-25% of your usual calorie intake for two nonconsecutive days of the week.  Then for five days of the week you eat as you normally would. By decreasing how much you eat two days a week, your average weekly intake is lower. For example, if you eat 2,000 calories a day for five days and 500 calories for two days your weekly average would be approximately 1,500 calories per day.

Pros

This may be easier to fit into your lifestyle than the alternate-day fast because you consume some food on those two days.  Some studies show that you may experience weight loss and a small improvement in metabolic function.

Cons

This requires planning and may be difficult to do long term.

Intermittent fasting should not be used to compensate for a poor diet or it could result in nutrient deficiencies.  There is little evidence that fasting results in improved metabolic health or in greater weight loss than with a regular calorie restriction diet.  Fasting can be difficult to do long term and it does not address behavioral changes, exercise or a healthy diet, which are essential to long term weight maintenance and optimal health.  This diet strategy may not be recommended with certain health conditions such as diabetes, gastrointestinal problems and eating disorders or while taking certain medications (e.g. insulin sensitizing or blood glucose lowering).  You should discuss with your doctor whether intermittent fasting is right for you.

By Jennifer Messineo, MS RD

Nick VanMeter