Eating one meal a day, known as the OMAD (One Meal A Day) diet, is a form of intermittent fasting popular for rapid weight loss and "detoxification." However, if not applied correctly, this method can pose numerous health risks, especially for individuals with underlying health conditions or high metabolic needs.

Those following the OMAD diet typically eat within a one-hour window and fast for the remaining 23 hours. This is considered an extreme variation of intermittent fasting. While on the OMAD diet, individuals can eat freely during their designated mealtime, without dietary restrictions. However, outside of this main meal, no calorie-containing foods, including milk in tea or coffee, should be consumed.

During the fasting period, individuals on the OMAD diet may drink black tea, herbal tea, or black coffee without sugar. Maintaining energy levels requires drinking sufficient water, approximately 2,5 liters daily.

Individuals on the OMAD diet can eat freely for one hour each day. Photo: Duc Hanh

Theoretically, OMAD can reduce overall daily calorie intake, support weight loss, and stimulate ketosis. It also increases fat expenditure as the body shifts from using glucose to lipids as an energy source, and can improve insulin sensitivity in some healthy individuals.

However, the OMAD diet is not suitable for everyone. Prolonged fasting can lead to low blood sugar, particularly in individuals with low liver glycogen levels, those engaged in high physical activity, or people with metabolic diseases such as diabetes. Dieters may experience fatigue, trembling, sweating, dizziness, and fainting.

Extended fasting can also cause stomach pain, bloating, and nausea, especially in individuals with a history of stomach or duodenal ulcers. This condition can further impair concentration, increase irritability, and disrupt sleep due to its impact on the central nervous system. While OMAD may promote rapid fat burning, if calorie intake is too low, the body risks losing muscle mass, leading to a less firm physique and affecting mobility.

Eating one meal a day is not a diet that can be sustained long-term. It is advisable to consult a doctor for advice and to assess your health status before choosing any diet plan. Individuals with type one diabetes, those who are pregnant or breastfeeding, children, adolescents, the elderly, and people with eating disorders should not follow the OMAD diet.

Doctor Vo Tran Nhu Thao

Endocrinology - Diabetes Unit

Tam Anh General Clinic, District 7