Taking a Break From Food?

Intermittent fasting weight loss method explored

/ Author:  / Reviewed by: Chris Galloway, M.D.

When people are trying to lose weight, they can spend a lot of time considering which foods are better to eat. Followers of a new weight loss method suggest people should spend more time not eating at all.

Intermittent fasting has been gaining attention as a weight loss and health plan, spurred in part by the publication of several popular books on the subject.

Proponents say it can aid in weight loss, help people live longer and protect the body against disease. But what is the science behind the method? And does it work?

The Basic Plan

Intermittent fasting is basically shifting back and forth between periods of eating food and periods of not eating food, known as the fasting period.

A review of what is known about intermittent fasting, led by James E. Brown, PhD, of Aston University in Birmingham, was published by The British Journal of Diabetes and Vascular Disease. In this review, the authors explained the details of the method.

“Intermittent fasting can be undertaken in several ways but the basic format alternates days of ‘normal’ calorie consumption with days when calorie consumption is severely restricted,” wrote Dr. Brown and team.

“This can either be done on an alternating day basis, or more recently a 5:2 strategy has been developed, where 2 days each week are classed as ‘fasting days’ (with less than 600 calories consumed for men, less than 500 for women).”

In a CMAJ (Canadian Medical Association Journal) article about the topic, previously covered by dailyRx News, it was explained, “Some advocates recommend fasting every day for up to 16 hours and consuming food only during a short ‘eating window.’

Others suggest going without food once or twice a week for 24 hour periods—having dinner one night, for example, and skipping breakfast, lunch and snacks the next day, then eating a normal dinner (no gorging).”

The Method to the Madness

To some people, the idea of not eating by choice for a 24-hour period sounds crazy. So what is the scientific reasoning that motivates proponents of the plan?

In an interview with dailyRx News, Deborah Gordon, MD, nutrition and homeopathy expert, explained the theory behind intermittent fasting.

"When we fast, our body follows a fairly predictable pattern of 'alternate fuels', starting with the easiest target: our muscle stores of glycogen," said Dr. Gordon.

The hope is that the body will quickly burn fat during these periods, aiding in weight loss.

According to CMAJ, it has been theorized that the mild “stress” put on the cells and body during fasting periods is similar to the stress put on the body during exercise.

“As long as you give your body time to recover, it will grow stronger,” explained CMAJ.

It is then thought that the body may be better able to protect itself, handle stress and potentially block disease.

From Theory to Real Life

Having a theory is all well and good, but can intermittent fasting help people lose weight and be healthier in real life?

So far, it seems the jury is still out. According to Dr. Gordon, how quickly fat starts burning during periods of fasting can vary widely from person to person, which could result in vastly different outcomes from fasting.

"If you are eating a low carbohydrate diet, or for other reasons have a low serum insulin, your body will happily, after about 8 hours, start to burn some fat – which is of course the goal of most dieters: fat loss is more important than weight loss," said Dr. Gordon.

"If, on the other hand, you have a high serum insulin (history of obesity, pre-diabetes, yo-yo dieting or just individual variation), your body is much more likely to burn fat very reluctantly, and turn to muscle consumption instead, leaving you weak, fatigued and hungry," she said.

According to Dr. Gordon, “A metabolism that knows how to burn fat actually tolerates short periods of fasting quite well, as the resulting ketone bodies suppress appetite.”

Dr. Gordon unintentionally experimented with intermittent fasting herself due to a travel schedule and sub-par airport food during a recent trip to Austin, and was pleased with the experience.

“Although I had previously been someone unable to skip a meal, I inadvertently fasted for 24 hours and actually felt fine, surprising myself and convincing me that, at least for me, consistently eating in a low carbohydrate fashion enabled me to skip meals and resort to fat burning for sustenance,” said Dr. Gordon.

But the fast can’t go on forever and Dr. Gordon reported, “Happily, there were some terrific barbecued ribs helping me break my fast.”

Concerns and Research Yet to Be Done

There is a fair amount of concern when it comes to intermittent fasting, and the plan can sound extreme to some.

CMAJ expanded on the concerns some experts have expressed, including, “If one already has a diet poor in vitamins and protein, eating less food could lead to vitamin deficiency and muscle loss."

Others are concerned that the plan could promote binge-eating on non-fast days and that the plan may be dangerous for people with a history of eating disorders.

According to CMAJ, “There is indeed a large body of research to support the health benefits of fasting, though most of it has been conducted on animals, not humans.”

In-depth human research about intermittent fasting is surely to be explored further, especially if the method continues to garner attention. This will hopefully help shed more light on this new method.

Dr. Gordon suggests that "...aspiring fasters check with their trusted medical advisor, as fasting can be quite beneficial and it can be, as the discussion points out, counterproductive."

Review Date: 
April 29, 2013