But OMAD is a restrictive eating approach that won’t necessarily appeal to everyone. If you’re following OMAD, you’ll need to take care not to overeat or overindulge on unhealthy foods during your main meal. You may also struggle to fit an entire day’s caloric intake into one large meal — or find yourself feeling uncomfortably full after eating this much in one sitting. There’s also a lack of research on the long-term effects of OMAD
Moreover, OMAD may actually be unsafe for certain groups of people. This includes people who are pregnant or nursing, who are younger than 18, and people who have an eating disorder or a history of disordered eating, says Moskovitz.
Shapiro also advises that people living with diabetes who are taking insulin should not follow this diet, as OMAD can affect blood sugar levels. In general, people with diabetes need to eat balanced meals regularly throughout the day, adds Moskovitz. “Going prolonged periods of time without eating can lead to harmful blood sugar lows followed by subsequent highs once a larger meal is inevitably consumed,” she explains. “This pattern of inconsistent eating can make it difficult to keep blood sugar levels low and stable.”
Finally, if you often have gastrointestinal (GI) issues like bloating or an upset stomach, OMAD may not be a good fit for you. This diet requires you to eat a lot of food at one time, which may cause GI discomfort.
Still, many people who are not in these categories will decide to move ahead with OMAD — and if you’re one of these individuals, know that careful planning is key. “If you’re going to attempt it, you still have to make sure you’re doing your best to eat balanced and nutritiously and make sure you’re still eating enough calories for the day if you want to stay healthy,” advises Moskovitz. “Fasting alone won’t be beneficial if [you’re] not carefully constructing the meals you’re eating in that time frame.”
Always speak to your doctor before starting a new diet, especially if you’re managing an underlying health condition or taking medication, or if OMAD represents a dramatic change in the way you eat.
If you are interested in trying OMAD but have not yet tried other types of IF, start slowly, suggests Shapiro. “Start with a 12-hour fast and then build up to 14 or 16 hours. Then try OMAD for a few days once you have eased your body into it,” she explains.