In recent years, intermittent fasting diets that involve restricting your eating window by extending your overnight fast have become increasingly popular as a way to lose weight and potentially improve health.
The OMAD diet, which stands for the One Meal A Day diet, is essentially an extreme version of a time-restricted intermittent fasting diet. Although plenty of people are gravitating towards the OMAD diet hoping to lose weight and boost health, there are also potential drawbacks of OMAD.
To learn more about the pros and cons of the OMAD diet and tips for following the OMAD diet, we spoke with Kimberly Gomer, MS, RD/LDN, a Registered Dietician and Director of Nutrition at Body Beautiful Miami.
The OMAD diet, short for the One Meal A Day diet, involves eating only one meal a day. Basically, it involves fasting for 23 hours and having an eating window of one hour or so.
Gormer says that the OMAD diet isn’t really a “diet” in the traditional sense of the word because a diet includes an eating plan, or certain foods you can and cannot eat.
“Instead, [the OMAD diet] is specifically targeted around the timing of meals — in this case, one meal per day,” says Gormer. “In its strictest application, people are to consume zero calories (allowing for water, black coffee, or tea) aside from the one meal they are entitled to eat for the day.”
Gormer says that while most people turn to the OMAD diet as a means for weight management, there are other potential benefits as well.
“The benefit for those who are trying to normalize insulin response, lower blood sugar, and/or lose weight is that it allows that body to have a metabolic rest. When no calories are consumed, there is not an insulin response,” she says.
Gormer goes on to explain that after we eat (and especially after eating foods high in carbohydrates), blood sugar increases as these nutrients are digested. This is a good thing because cells need glucose for energy, but they are unable to absorb it from the bloodstream without insulin. Insulin is a hormone that is produced and secreted by the pancreas in response to an increase in blood sugar.
“Insulin will act like a key that opens a gate and allows the cells to receive the sugar and then sends off the rest of the sugar for later use, meaning energy or fat storage in adipose, the fat cells,” explains Gormer. “When people are insulin resistant, that key gets sticky, and the cells do not get the sugar. The body senses a problem and calls out for more insulin.”
However, insulin can increase hunger. The more insulin that you have circulating in your body at any given time, the greater the chance that you will have an insatiable appetite.
“In the United States, an estimated 60 to 70 million people have insulin resistance, so the idea of limiting the timing and amount of insulin secretion [via the OMAD diet] makes sense for blood sugar response and weight loss,” notes Gormer.
Gormer says that the OMAD diet, by its very nature of eating only one meal a day, reduces your body‘s exposure to insulin and the frequency of insulin secretion, which in turn can reduce appetite and potentially improve insulin sensitivity.
Therefore, the weight loss effects of the OMAD diet are two-fold: not only does eating one meal a day typically reduce caloric intake by default because you are not grazing or consuming calories over numerous hours, but it can also help control appetite by decreasing insulin levels.
Gormer says the primary drawbacks of the OMAD diet are that it can potentially lead to binge eating or overeating and that it may be difficult to get in all of your nutritional needs.
Because people wait the entire day to eat and only have one opportunity to enjoy food, for some, this can psychologically trigger the desire to consume as much food as fast as you can, often at the detriment of making wise food choices. This can result in nutritional deficiencies and may not actually yield the weight loss results you’re hoping for, depending on how many calories you end up consuming and where they come from.
Furthermore, the OMAD diet is typically not recommended for athletes or people who exercise vigorously or for longer workouts because it is not usually possible to fuel your body appropriately before or after your workout.
Gormer says that, ultimately, the OMAD is too restrictive all around and not generally a sound approach to healthy eating.
“I believe while weight loss will happen if the person is compliant with the protocol, it will end up with overeating at some point due to the extreme restriction. The risk of the diet is that, once again, a person has high hopes of weight loss from this extreme plan and [is] disappointed when they restrict, lose some weight, and then gain it all back,” she warns. “The caloric restriction will happen when only one meal day is eaten, but many times, a lot of junk food is craved as the body tries to prevent this extreme restriction.”
Furthermore, Gormer believed the OMAD diet is not optimal for health because it usually does not result in lasting weight loss, and it may even cause metabolic damage if followed for an extended period of time.
“Repeated calorie restriction causes the BMR (Basal Metabolic Rate) to slow down, making it harder and harder to lose weight the more restrictive diets you follow. That is why diets may work initially but after a time, they seem to stop working,” she says. “For example, the BMR may be 2,000 [calories per day], but if that person diets, loses weight quickly, gains weight back and more, the next time they go on another diet, their BMR has slowed down due to the restriction from their last diet, so now their BMR is 1,800 calories. This cycle repeats to the point where people can’t lose weight no matter how much they restrict.”
Finally, one additional drawback of the OMAD diet is simply feeling very hungry and having low energy most of the day due to infrequent eating.
If you are going to follow the OMAD diet, it’s important to consume nutritious, satiating foods such as whole, unprocessed vegetables, lean proteins, healthy fats like nuts and seeds, and some whole grains and fruits.
Gormer strongly encourages people to seek healthier alternatives to the OMAD diet.
“The best thing for health is avoiding processed foods, including packaged foods loaded with sugar, processed grains, and highly processed vegetable seed oils (soybean, corn, canola, rice bran, sunflower, safflower, and vegetable). Instead, stick to whole foods like protein, vegetables, healthy fats (like avocado and olive oil), and limited carbohydrates (whole fruits and grains) depending on your lifestyle, exercise habits, and individual metabolism,” advises Gormer. “Avoiding fad diets, fasting, and too much restriction to avoid metabolic damage is key.”
In terms of the timing and frequency of eating, Gormer suggests limiting snacks and just going for three meals a day if something like the OMAD diet is appealing to you for insulin reasons. Finally, she suggests working with a registered dietitian and a nutritionist who can help support you with your diet and health goals and tailor an individual eating plan that makes sense for your body and your life.
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