Fasting: Fad or health promotion strategy?

Posted April 19

Fasting can generally be thought of as a period of limiting or abstaining from consuming food. Throughout human history, unintentional fasting occurred naturally when food was scarce and was compensated for by large meals when food was abundant. In addition, many religions still include intentional fasting as part of traditional practice. So is fasting a thing of the past or is it here to stay?

Today, while most Americans have plenty of food available, some wonder if fasting should be a more regular part of our modern eating habits for health reasons. In recent years, concerns regarding obesity and other chronic diseases such as cardiovascular disease and diabetes have driven research to find effective ways to combat these significant public health issues. As part of this search for effective and safe health promotion strategies, the practice of intentional fasting has gained more attention.

Typically all fasts focus on some level of significant calorie restriction on “fasting days” and a return to more normal eating habits on “non-fasting” days. Some fasts may focus on limited time frames such as a day or two during a specific time of year where other approaches suggest fasting on a weekly basis. Not all fasts are low-calorie, and some approaches suggest compensating by eating moderately more than daily needs on non-fasting days.

Fasting approaches studied in recent research include intermittent fasting, alternating day fasting and alternate day calorie restriction. Much of this research has been conducted as part of animal studies that may not be applicable to humans. However, some of the research with human subjects does suggest benefits from certain types of fasting such as weight loss and improvements in cardiovascular risks and glycemic control.

In addition to potential physical benefits, some positive short-term effects of fasting on mental health have also been seen. This could be based on a release of the body’s “feel good” chemicals called endorphins during a fast. These are the same chemicals released during prolonged exercise leading to the phrase “runners’ high.”

While the research has been increasing, there are still a wide variety of fasting approaches that have not been studied sufficiently to determine their effectiveness or safety. In particular, there are fasts that are restrictive “fad” diets that present dangers to health. Extreme and restrictive eating patterns have the potential to contribute to nutrient deficiencies and to the development of serious health conditions such as eating disorders.

In addition to potential effects on health, it’s also important to consider the practical side of fasting and how it affects the quality of daily life. The experience of fasting can vary widely between individuals. Some people report feeling dizzy, having low energy and/or mood and having headaches when going without food for too long. This can make it difficult to participate in regular daily activities or to be physically active.

On the other hand, some people may report positive feelings while fasting such as improved mental focus or physical energy. Others are willing to put up with some of the discomfort on fasting days in order to “jump-start” a healthier lifestyle or to reduce calorie intake by focusing weight management efforts on certain days. This may allow individuals to eat “normally” on other days and still maintain a healthy weight.

Regardless of the positive and negative sides, one of the main issues with fasting as a health promotion strategy, as with all restrictive diets, is that many people find it difficult to stick with for the long run. A healthy lifestyle is ultimately about the way we eat, move and live on a daily basis. Making changes that we can’t see being a part of our daily life in the years to come may not actually be promoting health. It could lead us to frustration and a feeling that living a healthy lifestyle is just too hard.

Given all of this information, for those still considering fasting, consider these suggestions as a staring point:

  • In general, fasting is not recommended for those at nutritional risk and certain populations such as children, women that are pregnant or breastfeeding, or anyone with an eating disorder or struggling with disordered eating.
  • Always check with your doctor before significantly changing your eating habits to ensure safety and make sure any medications or other aspects of your health care plan won’t be negatively affected.
Consider testing out a more moderate approach to gradual healthy eating changes and becoming more aware of hunger and fullness signals.

  • Try exploring the experience of hunger by prolonging time between eating and learning to be more comfortable with mild physical hunger from time to time.
  • Improving hunger awareness, such as by eating when physically hungry and stopping when satisfied, may help individuals moderate their food intake and reach a modest level of calorie reduction and avoid overeating.


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