Influencer Choi Jun-hee's 16-hour fast: What intermittent fasting can and can't do

Influencer Choi Jun-hee has said she maintains a weight of around 42 kilograms by fasting for 16 hours a day — a window that recently stretched to 18 hours. The so-called 16:8 method of intermittent fasting, in which eating is confined to an eight-hour window, is widely recognized as a weight-management tool, but experts caution that simply extending the fasting period does not produce proportionally greater fat loss.

On Tuesday, Choi posted a video to her SNS account under the caption "The real weight-maintenance life of a married woman who lost 55 kilograms," documenting her daily routine.

In the video, she prepared a meal using green onions, chicken and other ingredients. She said she normally practices 16:8 intermittent fasting — fasting for 16 hours and eating within the remaining eight — but that on that particular day the fast had run longer than planned, reaching 18 hours.

Choi said she regularly takes supplements and inner-beauty products, which she credited with suppressing her appetite and making the fasting hours pass without notice. She also urged followers to "eat well enough to avoid hair loss while losing weight."

The 16:8 approach is the most common form of time-restricted eating, in which all meals are consumed within an eight-hour window and no caloric food or beverages are taken in during the remaining 16 hours of the day.

Confining meals to a set window naturally reduces late-night snacking and between-meal eating, which can lower total daily caloric intake. Some research has observed improvements in body composition markers such as weight and waist circumference as a result.

A 2025 study highlighted by the US National Institute on Aging found that obese adults who limited their daily eating window to eight hours showed weight loss and modest improvements in certain cardiovascular and metabolic markers over 12 months. However, whether meals were eaten earlier or later in the day made little difference to the outcome.

It is also difficult to conclude that intermittent fasting is decisively superior to conventional caloric restriction. A recent review of randomized trials involving overweight and obese women found that time-restricted eating aided weight loss but showed no clear advantage over simple calorie-restricted diets.

Choi had previously explained her approach by saying that "if you stick strictly to the fasting window, your body has no new energy coming in, so it pulls out and burns stored body fat."

While it is true that the body draws more heavily on stored energy during a fast, that alone does not determine how much body fat is lost over time. What ultimately matters is the balance of energy consumed and expended over days and weeks, along with diet quality and physical activity levels.

Extending the fast from 16 to 18 hours, or from 18 to 20, does not therefore guarantee greater fat loss. On the contrary, a prolonged fast can trigger overeating at the next meal or make it harder to meet nutritional needs — both of which can undermine long-term weight management.

The fasting window is not the only noteworthy aspect of Choi's video. After breaking her fast, she prepared a meal herself using chicken, green onions and other ingredients — a reminder that what is eaten during the eating window matters just as much as when.

Protein-rich foods such as chicken help preserve muscle mass and sustain satiety during weight loss and maintenance. Adding plenty of vegetables increases dietary fiber, vitamins and minerals while adding volume to a meal.

Cutting the number of daily meals too drastically, on the other hand, can make it difficult to meet needs for protein, iron, calcium and essential fatty acids. Staying the same weight on the scale means little if it comes with persistent fatigue, declining physical performance or loss of muscle mass.

Particularly for those who have already lost a significant amount of weight and entered a maintenance phase, the priority should shift from continuing to reduce intake toward preserving muscle, fitness and nutritional status at the current weight.

Anyone who repeatedly experiences dizziness, cold sweats, severe headaches or difficulty concentrating while fasting should not push through an extended fast. People taking diabetes medication, those who are pregnant or breastfeeding, and those with a history of eating disorders should consult a medical professional before starting intermittent fasting.

Choi's advice to "eat well enough to avoid hair loss while losing weight" touches on an important and often overlooked aspect of weight management.

Rapid or significant weight loss, or a sharp drop in caloric intake, can trigger telogen effluvium — a condition in which more hair than usual falls out several months later. The American Academy of Dermatology notes that excessive hair shedding can follow substantial weight loss.

This does not mean that dieting inevitably causes hair loss. However, extreme caloric restriction combined with deficiencies in protein, iron or other nutrients can affect hair growth.

If hair begins falling out noticeably during a weight-loss effort, it is worth examining the pace of recent weight loss, daily food intake, protein consumption and the possibility of anemia before reaching for hair-loss products. Shedding that persists for several months or results in patchy thinning warrants a visit to a dermatologist.

Supplements and inner-beauty products cannot substitute for meals. The US Food and Drug Administration cautions that dietary supplements should not replace a balanced diet, and that some ingredients can interact with medications or cause side effects. Some weight-loss supplements have also been found to contain undisclosed ingredients, making it important to check labels and dosages carefully.

The more instructive takeaway from Choi's routine is not the 18-hour fasting figure itself, but the consistency with which she manages her eating window and the attention she pays to protein and vegetables when she does eat. Intermittent fasting is one of several tools available for weight management — and the real measure of a sustainable approach is not how long a person can endure a fast, but whether they can eat enough and still maintain it over time.