Entrepreneurs, venture capitalists and a variety of celebrities have extolled its virtues in helping them lose weight, while medical experts are intrigued by the possibility that it may enhance cognitive functioning and longevity and help treat and prevent some diseases.
As researchers study the different fasting mechanisms to determine the ideal protocol for a variety of outcomes in a variety of populations, however, the general public must proceed by trial and error.
That leaves dietitians such as myself concerned that the hype around fasting could encourage people to follow harmful plans that severely restrict nutrients, cause stress or unsuccessfully treat serious conditions.
And there are many
-Intermittent fasting means eating normally four or five days a week and consuming minimal calories on two or three nonconsecutive days.
-Time-restricted eating requires setting a window for consuming food, such as 7 a.m. to 7 p.m, and having nothing but noncaloric liquids the rest of the time.
-The “fasting-mimicking diet” involves eating a small number of calories daily for a specific period of time – say, five consecutive days every other month.
These protocols all have benefits and drawbacks. One approach may work well for some yet be entirely unsustainable for others.
Although it’s possible that fasting helps manage blood sugar and insulin, fight inflammation and ease sleep problems, most people follow a fasting diet to lose weight.
Fasting is believed to help in this goal because of the effects that caloric restriction and extended periods without food have on metabolism, or simply because people eat less during the restricted-feeding window.
(Some dieters benefit from the structure and clear boundaries that fasting plans offer.)
The problem is that too many people jump on the fasting bandwagon without understanding how to assess its impact.
Once a plan has been integrated into your everyday life, you should take time every week or month to analyze how things are going.
Even if weight loss is your primary goal, it’s important to consider how fasting is affecting other aspects of your health, such as your energy levels, ability to exercise and digestion.
If it isn’t, the answers can also provide clues about where you can tweak your plan – or help you decide that, despite the endorsements from Beyoncé and Hugh Jackman, fasting simply does not work for you.
Berman is a registered dietitian and a personal trainer.