What Is the OMAD Diet? Everything to Know About This Intermittent Fasting Method (2024)

The One Meal a Day (OMAD) diet is an intermittent fasting method that instructs you to fast for 23 hours and then consume one large meal in one hour. Proponents of intermittent fasting say that not eating for prolonged periods is an effective weight loss method. Some evidence suggests that the diet helps prevent and treat chronic illnesses like diabetes.

Still, others say that intermittent fasting might be harmful. The OMAD diet may result in fatigue and severe hunger that causes you to overeat. Read on to learn about the OMAD diet and whether it can help you reach your weight loss and health goals.

With intermittent fasting, you consistently switch between periods of fasting and eating. The OMAD diet is an extreme type of intermittent fasting in which you fast for 23 hours and eat for one hour.

Like many diets, OMAD has a host of rules. To stay consistent, you must plan your one-hour eating window within the same four-hour time block daily.

You do not need to consider your calories or worry about the nutritional profile of your food. Your one meal may consist of any food you like, as long as you save all of your calories for that one period,Natalie Rizzo, RDN, a dietitian based in New York and author of "The No-Brainer Nutrition Guide For Every Runner," toldHealth. Still, you must consume your meal on nothing larger than a standard dinner plate. Whatever you eat cannot rise above three inches on your plate.

The OMAD diet allows you to drink beverages during your 23-hour fast. Your beverages must be calorie-free, like black coffee or water,Dana Angelo White, RDN, a sports dietitian based in Connecticut and author of "Healthy Instant Pot Cookbook," toldHealth.

Does It Lead to Weight Loss?

There's a lack of research on whether the OMAD diet is an effective and safe weight loss plan.Still, some evidence suggests fasting for long periods, as with the OMAD diet, might help you lose weight. You drastically reduce your calorie intake by restricting your eating time, leading to weight loss.

A review published in 2022 found that "metabolism switching" is another way intermittent fasting helps you lose weight. Your body starts burning fat if it runs out of sugar, its primary energy source.

Beyond weight loss, intermittent fasting might protect against or treat chronic illnesses like:

• Age-related neurodegenerative disorders (e.g., Alzheimer's disease)
• Heart disease
• Some types of cancer
• Type 2 diabetes

Possible Risks and Side Effects

Lengthy fasting periods may cause severe hunger, leading you to overeat and gain weight. No food is off-limits for your one-hour meal, so you might opt for high-fat foods to satisfy your appetite when it's time to eat. You may take in more calories than you need if you indulge in high-fat, low-nutrition foods.

"When someone deprives themselves of food for 24 hours, they tend to lose control and overeat when it's time to eat again," said Rizzo. "This can lead to choosing unhealthy options and eating way more than what feels natural in one sitting."

Getting enough nutrients your body needs in one meal might be tough, said White: "Sure, a well-balanced multivitamin and omega-3 supplement would be helpful, but I would still have concerns about dieters meeting their needs."

Not eating for 23 hours may cause symptoms like:

• Dizziness
• Fatigue
• Headache
• Low blood sugar (hypoglycemia)
• Nausea
• Trouble sleeping
  

During fasting periods, you may consume beverages with no calories, such as black coffee and water. The OMAD diet does not restrict foods during your one-hour eating period. Still, experts advise that you opt for a balanced, healthy meal.

"The diet allows you to eat whatever you want," said Rizzo. "Personally, I would suggest a well-balanced meal with healthy carbs, protein, and healthy fats."

You are likelier to gain or not lose weight if you eat high-calorie, high-fat foods during your eating periods. In contrast, research has found that choosing foods on the Mediterranean diet for your eating period assists with weight loss and helps manage diabetes.

The Mediterranean diet includes foods like:

• Fruits
• High-fiber foods
• Lean meats
• Nuts and legumes
• Olive oil
• Seafood
• Vegetables
• Whole grains

Adding variety is essential to get enough nutrients, said White: "Mix it up by eating different things every day, so you don't miss out on nutrients."

Should You Try the OMAD Diet?

Experts do not advise intermittent fasting to lose weight or treat health conditions like diabetes. There's a lack of research on whether not eating for prolonged periods is safe and effective. The effects of the OMAD diet in pregnant and breastfeeding people and those with a history of eating disorders are unknown.

"I would not recommend this diet," said Rizzo. "I think it's entirely too restrictive and can lead to choosing unhealthy options. If I starved myself all day, I would be more inclined to eat a pizza than a piece of fish with veggies."

Still, the OMAD diet might work for some people and be harmful for others. Talking to a healthcare provider before trying the OMAD diet is best.

Intermittent fasting might be especially risky for people with certain health concerns or who take specific medicines. Research has also shown that people who fast for prolonged periods have a higher risk of gallstones than others. Gallstones are hard pebbles in your gallbladder and cause pain, nausea, and vomiting.

The OMAD diet is an extreme intermittent fasting method that restricts your eating periods to only one hour per day. Some evidence suggests that prolonged periods of not eating might result in weight loss. Still, experts say that this type of intermittent fasting may result in fatigue and severe hunger. In the end, you might gain or not lose weight.

Talk to a healthcare provider before trying the OMAD diet. They can help you find a weight-loss program that involves eating balanced, healthy meals and staying physically active.