The Truth About the 1,000-Calorie-a-Day Diet for Weight Loss

Emily Shiffer

August 9, 2024 at 3:58 AM·4 min read

Counting calories and creating a calorie deficit are some of the more successful tactics people use when trying to lose weight. But if you are considering drastically reducing your caloric intake to just 1,000 calories per day, experts agree that you will probably do more harm than good.

Although we've been trained to think of calories as "the enemy" thanks to toxic diet culture, calories are energy, and we need them to survive. In fact, the 2020-2025 Dietary Guidelines for Americans include an estimated calorie needs of 1,600 to 2,400 calories a day for females and 2,000 to 3,000 calories a day for males.

"These numbers, however, do not take into consideration your physical, medical or emotional needs. Diets should be individualized, not a one-size-fits-all approach," notes Bonnie Taub-Dix, RDN, creator of BetterThanDieting.com.

So while 1,000 calories might seem like a good benchmark (and it's a number that's easy enough to remember), there are a few things you should know before you try it.

Is the 1,000-Calorie-a-Day Diet Safe?

A 2013 study suggested that prescribing 1,000-calorie diets versus 1,500-calorie diets is more likely to result in significant weight loss for obese individuals.

While low-calorie diets may lead to weight loss, not eating enough calories can have a negative impact on the body—and if you are trying to eat just 1,000 calories per day, it is not safe, according to registered dietitian Jonathan Valdez, RDN, owner of Genki Nutrition and a spokesperson for the New York State Academy of Nutrition and Dietetics.

Short-term risks of eating just 1,000 calories or fewer a day can include:

Dizziness
Fatigue
Gallstones
Headaches
Hunger
Nausea
Nutrient deficiencies

Longer terms risks of a 1,000-calorie diet can also include:

Slower metabolism, which leads to plateauing or even slower weight loss results
Weakened bones (especially if you exercise while on such a low-calorie diet)
Regaining weight you lost (and possibly even more than that) after restarting a normal diet

Unfortunately, for most people, a diet of 1,000 calories per day is likely to backfire.

"That initial weight loss might make it seem like your diet is 'working,' but when you're feeling deprived and the pounds are not pouring off, there’s a tendency to give up and go back to the habits that you were trying to escape in the first place," adds Taub-Dix. "For example, if you ate just 1,000 calories worth of chocolate cake every day, you'll probably lose weight, but you might also lose your hair, your teeth and your interest in the chocolate cake after a while!"

A real long-term risk of low-calorie diets is gaining the weight right back (and then some), especially when your diet is as restrictive as this one. A 2015 long-term outcome study found that one-third of dieters may regain more weight than they originally lost once they go off of their diets.

Is the 1,000-Calorie-a-Day Diet Effective for Weight Loss?

Here's where it gets tricky for some to understand: One 2013 study of 125 women with obesity over the course of a year showed that on average, participants on a 1,000-calorie-a-day diet for a year lost more weight at a more rapid pace than participants on a 1,500-calorie diet. However, at the end of the study, those with the 1,000-calorie limit gained back significantly more weight that they'd lost than the 1,500-calorie limit group did.

The study's authors noted that the 1,000-calorie diet is likely too difficult to maintain over long periods of time, and that certain participants in the 1,000-calorie program didn't even lose more weight than their 1,500-calorie co-participants. One recommendation from the study's authors was for patients with obesity to possibly start with a 1,000-calorie-a-day diet to kickstart their weight loss towards their health goals, then gradually increasing caloric intake over time to 1,250 calories and then 1,500 calories, while integrating crucial lifestyle changes to make their weight loss sustainable.

All that said, never do anything of the sort without consulting with your physician or care team first! Everyone's needs are different, and your health is so much more important than a number on a scale (or on the tag of your pants).

The Bottom Line

A 1,000-calorie diet is likely to have more negative effects than positive ones and is not recommended by registered dietitians. However, if you are looking to lose weight, experts suggest working with a registered dietitian/nutritionist who can help you create a meal plan to help you lose weight in a calorie deficit in a safe and healthy way.

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