Son Dam-bi, who shed 21 kg after childbirth, fires back at Mounjaro rumors: 'Don't dismiss my effort'

Singer and actor Son Dam-bi, who made headlines for reportedly losing 21 kilograms after giving birth, has shared the habits behind her postpartum body transformation — and pushed back sharply at online speculation that she used the weight-loss drug Mounjaro. The three pillars she cited were consistent movement, fasting between meals, and allowing herself occasional indulgences.

Son recently posted on her Instagram account, listing what she called "three habits for getting my body back after childbirth": moving consistently, even if only briefly; maintaining a 16-hour fast; and eating the foods she craves in moderation.

"On days I worked out, I focused on the workout. On days I couldn't make it to the gym, I moved around at home whenever I had a moment," she said. "Rather than skipping exercise entirely just because I didn't have a long stretch of time, I tried to move a little, as often as I could."

She added that she keeps fasting periods between meals. "Instead, I make sure to eat two proper meals a day," she said, and went on to say, "I don't cut out all the foods I love. I eat what I want in moderation, then try to return to my normal diet from the next meal onward."

When a commenter suggested she had used Mounjaro, Son fired back. "I lost weight through consistent exercise and diet management. I'd appreciate it if people didn't so easily pass judgment on someone else's effort," she said. When the commenter apologized, she extended an olive branch: "It's fine. After having a baby and losing a lot of weight, muscle doesn't build easily even with a lot of exercise. It hasn't been that long since I gave birth, so I'll keep working at it."

The 16-hour fast Son described is widely known as the "16:8" method of intermittent fasting, a popular approach to weight management in which eating is confined to an eight-hour window each day.

Research cited by the US National Institute on Aging supports its benefits: a 2025 study found that obese adults who restricted their eating to an eight-hour window showed weight loss and improvements in some cardiovascular and metabolic markers over 12 months.

However, intermittent fasting does not appear to be meaningfully more effective than conventional calorie restriction. A recent study pooling randomized trials involving overweight and obese women found that time-restricted eating did help with weight loss, but produced no significantly greater reduction than a standard calorie-restricted diet.

In a related line of research, a team led by Dr. Daniel Ostendorf at the University of Colorado found that a so-called "4:3" intermittent fasting pattern — fasting three non-consecutive days a week and eating normally the other four — was effective for weight loss. The finding suggests that daily fasting is not necessary as long as overall calorie intake is reduced.

Published in the Annals of Internal Medicine in April last year, the study randomly assigned 165 adults aged 18 to 60 with a body mass index between 27 and 46 to either a 4:3 intermittent fasting group (84 participants) or a daily calorie restriction group (71 participants), then compared weight-loss outcomes over 12 months. BMI is calculated by dividing body weight in kilograms by the square of height in meters.

South Korea classifies a BMI of 23 to 24.9 as "pre-obese" (overweight or at-risk weight) and 25 or above as "obese," following World Health Organization standards for the Western Pacific region — meaning all participants would be considered obese by Korean criteria.

The 4:3 fasting group cut their daily calorie intake by 80 percent on three non-consecutive days each week and ate without restriction on the remaining four days. The daily calorie restriction group reduced their daily energy intake by 34 percent, keeping their total weekly calorie consumption equal to that of the fasting group.

Both groups also stayed consistently active throughout the study period — as Son herself recommended. All participants took part in an intensive behavioral weight-loss program that encouraged them to build up to at least 300 minutes of moderate-intensity physical activity per week over the 12 months.

As a result, the 4:3 fasting group lost an average of 8 percent of their body weight after 12 months, compared with an average 5 percent loss in the daily calorie restriction group. The fasting group also showed greater improvements in cardiovascular and metabolic health markers, including systolic blood pressure, total cholesterol and fasting blood glucose levels.

The question of which days to fast raises a related one: which hours of the day?

Some experts have warned that skipping breakfast in the name of intermittent fasting may actually be counterproductive for weight loss.

According to The Guardian in January last year, Dr. Emily Leeming, a nutritionist at King's College London, said many people skip breakfast for intermittent fasting, but that this is not advisable. "There is research that contradicts the claim that skipping breakfast leads to weight loss," she said. "Our ancestors tell us that meal timing should align with daylight hours — eating breakfast and dinner early, and avoiding late-night meals."

The argument is that eating during the day, when the body's digestive organs are most active, and fasting at night, when digestive function slows, is the more beneficial approach.

Leeming said skipping breakfast can lead to more snacking and larger, less healthy meals in the evening. "Research shows that people who skip breakfast tend to fall short on fiber, essential minerals and vitamins, and are also more likely to experience depression and stress," she said.

Meanwhile, research has also suggested that intermittent fasting may be harmful for older adults, potentially accelerating the accumulation of chronic diseases — a reminder that this approach to weight management warrants careful consideration regardless of timing or circumstance.

Last August, a team led by Dr. Adrián Carballo-Casla at the Karolinska Institute in Sweden tracked about 2,900 elderly Swedes for up to 15 years and found an association between habitually long gaps between meals and a faster accumulation of chronic diseases, Yonhap reported at the time. The findings were published in the Journal of Internal Medicine.

The pattern was particularly pronounced among adults aged 78 and older, where longer habitual meal intervals were associated with a faster buildup of multiple chronic conditions over time. The team said the health effects of eating patterns that involve extended gaps between meals — such as intermittent fasting — deserve close attention in older populations.

The researchers said the results suggest that the health benefits of intermittent fasting, which have largely been studied in younger populations, cannot be assumed to apply equally to older adults.

However, they cautioned that because the study was observational, it could not establish a causal link between long meal gaps and increased chronic disease, and that the findings should not be interpreted as proof that intermittent fasting is harmful to older people.

Their overall conclusion was that "among older adults, particularly those aged 78 and above, habitually long intervals between meals were associated with a faster accumulation of chronic diseases," adding that "this suggests that prolonged fasting may potentially be harmful in old age."