Noom recommends people stick to 1,200 calories a day. That can cause serious side effects, according to a dietitian.

Noom recommends people stick to 1,200 calories a day. That can cause serious side effects, according to a dietitian.
Crystal Cox/Business Insider
  • The popular weight loss app Noom brands itself as different from diets, but sets a low calorie goal.
  • For many users, the 1,200 calories a day limit is too few and can cause side effects, a dietitian says.
  • Symptoms of undereating can include fatigue, mood swings, brain fog, and disrupted metabolism.

Noom, a weight loss app that earned $400 million in revenue last year, brands itself as different from a regular diet, according to ads, using psychology to help customers change their lifestyle.

But the app's default recommendation of 1,200 calories a day for many users, regardless of body type or weight loss goal, could lead to side effects, according to a dietitian.

Cutting calories too low can cause mental and physical fatigue as well as risk of serious health conditions over time, registered dietitian Brigitte Zeitlin told Insider.

1,200 calories a day is the recommendation for toddlers, not adults, experts say

Noom users are encouraged to track their food and to stay within a certain calorie range, set to 1,200 for many users, several of whom spoke to me about the diet. I was assigned a 1,200-calorie goal when I tried the app myself.

I'm an active person who lifts weights and does high-intensity exercise six days a week. This was more than 800 calories below the minimum intake recommended for me by the Mayo Clinic and MyFitnessPal.


"That's extremely low. It's not really an adult serving size," Zeitlin said.

1,200 calories is the recommended amount for a toddler, according to a dietitian who reviewed the app for the Seattle Times.

Noom says its much debated 1,200-calorie recommendation is just a suggestion, and that users can adjust their weight loss goals, which will change their calorie limits. Even after I adjusted for the slowest possible weight loss, my daily calorie goal increased to only 1,420. I was told I could "earn" more by meeting my "step goal," the number of steps I took in a day.

Christine Byrne, a dietitian and journalist in North Carolina, said that after tweeting and writing about Noom, she received hundreds of messages from Noom users. Byrne wrote that all but three of the Noom users who contacted her said they'd been assigned a 1,200-calorie goal. Three women said they'd signed up for Noom while they were breastfeeding and got that goal, despite recommendations from the Centers for Disease Control and Prevention that they eat more.

Calorie needs can vary based on activity level and current weight

Losing weight requires a calorie deficit, burning off more calories than you eat.


Some people may need fewer daily calories for weight loss, Zeitlin said, depending on gender, body size, and exercise habits.

Zeitlin said the app doesn't seem to account for individual calorie needs or differences.

"The problem with Noom is that they're not giving you that number based on you," Zeitlin. "The right calorie amount to lose weight is different for everyone. There shouldn't be a standard. It's detrimental, unrealistic and restrictive."

Undereating can cause fatigue, brain fog, hair loss and moodiness

While a small calorie deficit leads to weight loss, cutting calories too severely can have immediate side effects, Zeitlin said, including:

  • Fatigue
  • Brain fog and memory lapses
  • Hair loss
  • Dry or red skin
  • Digestive issues
  • Irritability and moodiness

Long-term calorie restriction can disrupt your metabolism and increase the risk of illnesses

Depriving the body of essential nutrients by undereating, particularly if you drop below 1,000 calories a day, can cause more dangerous symptoms over a period of months or years, including:

  • Stress on the internal organs, including the heart
  • Increased risk of bone fractures
  • Weakened immune system
  • Disrupted metabolism

Severe calorie restriction can also be a risk factor for life-threatening problems such as heart failure over time.

"How long before you end up in the hospital depends on how lucky you are," Zeitlin said.

The app doesn't have a system for flagging high-risk behaviors or disordered eating history

Another potential risk of very low calorie diets is that they could trigger people with a history of disordered eating, Zeitlin said.

When I signed up for Noom, the process didn't include any questions to screen for this or other factors that might require more specialized attention.

"Apps might be helpful to learn new strategies to stick to your diet, but if you're having more severe issues, you really need specialized treatment," Dr. Robert Hindman, a psychologist with the Beck Institute, told Insider. "I don't know if they have a mechanism for kicking you off and saying you should really see someone for this."


The risk of triggering disordered eating behaviors isn't unique to a 1,200 calorie diet, however.

Zeitlin said any type of restrictive diet can be a trigger, regardless of the specific calorie limit.