Intermittent Fasting and Health

In this article, I would like to share my findings on a dietary approach known as intermittent fasting, which has received much attention in the last several years for its potential to promote weight loss and improve insulin sensitivity, glucose control, and blood lipid levels. Readers of this article should consult with their health care provider before making any significant dietary changes.

Presently, the social norm in Western culture is to consume three or more meals each day. As a result, most of each 24 hour day is spent in a postprandial (time after a meal is consumed), fat-storing state.¹

Daily calorie restriction (daily energy intake that is reduced to 70-75 percent of estimated energy needs) has been widely studied for its potential to assist in weight loss and improve health.² Due to the lack of long-term adherence to daily calorie-restricted diets and the tendency to regain the weight that was lost, alternative dietary approaches continue to be investigated.²

What is intermittent fasting?

Intermittent fasting includes several types of fasting regimens in which there are periods when there is no caloric intake. Water is always allowed.

Three of the most common types of intermittent fasting include:

Alternate day fasting

• Unrestricted feeding days alternated with fasting days.
• Fasting days often allow up to 25% of baseline energy needs. Calories consumed on fasting days may be permitted over the day or restricted to a set time frame (such as 12 PM to 2 PM).^3,4

5:2 fasting

• Calories are restricted to 25% of baseline energy needs two days each week.
• Fasting days may be consecutive or non-consecutive.
• Non-fasting days (5 days/week) allow for unrestricted feeding.^3,4

Time-restricted feeding

• Caloric intake is allowed for up to 8 hours during the day.
• During the feeding timeframe, calorie intake is unrestricted.
• The fasting timeframe takes place over 16 hours, typically from the evening to late the following morning.^3,4

The benefits of intermittent fasting

• Improved diet adherence
• Weight loss
• Maintenance of fat-free mass (i.e., lean body mass)
• Appetite regulation better managed
• Improved metabolic and cardiovascular markers of health (i.e., blood glucose, A1c, blood lipids, blood pressure, and inflammatory markers)^4,5,6,7,8

Based on the available evidence, intermittent fasting and daily calorie-restricted diets appear to be similar in their effectiveness for achieving weight loss and improving metabolic markers associated with type 2 diabetes and cardiovascular disease.^7,8

More research on the topic of intermittent fasting is needed to assess the long-term safety and sustainability of this eating regimen.