Getting healthy can be challenging—especially if part of your health journey involves losing weight. It’s tough to differentiate sustainable lifestyle changes from fad diets and quick-fix promises, which can lead to an endlessly frustrating, rinse-repeat cycle of hopping from one weight loss trend to the next.
A diet app isn’t a one-way ticket to health. (Our bodies are a lot more complicated than that.) But depending on your goals, lifestyle, and medical history, a diet app may help with some health-promoting aspects of weight loss, including finding healthy recipes, gaining information about portion control, and growing awareness about what you’re eating.
To find the best diet apps, we tested some of the most popular options on the market, evaluating them for safety, customization, ease of use, efficacy, and dietary education. By the end, Noom emerged as the best option thanks to its focus on whole foods, healthy lifestyle updates, and moderate changes.
Here’s how the best diet apps stack up:
- Weight Watchers / WW
The Best Diet App
- 4.7-star rating on iOS and 4.3-star rating on Google Play
- Provides nutrition and behavior education
- Flexible and positive messaging
- Easy to use
- Green/yellow/red labeling feels restrictive
- Super long questionnaire didn’t seem to create noticeable change
Of all the apps on this list, Noom seemed to have the strongest focus on whole foods, behavioral education, and humane calorie goals. We also appreciated its model of “progress not perfection” and its encouragement to include foods from all groups.
Noom had the most extensive setup of all the apps we tested. The SAT has fewer questions. Once you’re in the app, there’s a simple interface that provides educational “mini courses” and allows you to track meals, exercise, weight, and water intake. The educational articles, for the most part, seem to be rooted in both nutrition science and behavioral science. And they were honestly fun and easy to read.
The app encourages making incremental improvements, such as slowly building up your daily steps, rather than aiming for 10,000 from the start.
One feature I appreciated was rather than giving a single calorie target (for example, 1,500 calories per day), it provides a range. The range it provided was 1,350 to 1,940 calories per day–the most generous of any of the apps. It also encourages users to eat toward the higher end of your calories—or even beyond them—if you feel hungry. And the zone adjusted based on any activity you log, including steps, which were automatically synced from my phone (as they were with all the other apps we tested.) Noom allows you to adjust your calorie windows, but it doesn’t allow users to adjust calories below 1,200 per day for women and 1,500 per men—an encouraging feature considering one of the other apps we tested.
Still, a few things felt disappointing. First, all those questions at the beginning? The full-out personality test? These didn’t seem to factor into any kind of customization in the app beyond a basic calorie count.
Second, the app has a heavy focus on eating more foods that will help you feel full with fewer calories (largely plant-based, water-heavy foods; Noom literally calls water a “miracle ingredient”). Ultimately, it’s information that may or may not feel novel, depending on how much you already know about nutrition: make your wrap with collard greens instead of a tortilla; eat grapes instead of raisins.
To further this concept, Noom uses the idea of “stoplight” foods, so each type of food has a color: green, yellow, or red. The colors are based on caloric density—literally the number of calories divided by the weight of the food. Green foods are low caloric density, yellow are medium caloric density, and red are high caloric density. The app explicitly says you should be eating all of these foods—it recommends 30% green foods, 45% yellow foods, and 25% red foods.
But this mental trick doesn’t always seem to work. Plenty of healthful foods are considered calorie dense, so calorie density isn’t a perfect measure of healthy food choices. My brain immediately associated yellow and red with “bad” or “less good.” At the very least, I wish Noom had chosen more neutral colors (like purple or blue), since there are so many healthy foods in those categories. Yellow foods include beans, chicken, tuna, salmon, and avocado, for example. Red foods include nuts and seeds.
Noom also waits an entire week to give you suggestions based on the proportions of green/yellow/red foods you input—that felt like a long time, considering it was happy to provide meal-by-meal calorie counts. I would have loved to see “try adding a few red foods into your next meal” or “you could use a few more green foods in your snack” after logging my meals.
When they finally showed up, it felt getting graded on an essay you’d forgotten you’d written—not super useful. The feedback also contradicted a lot of what Nooom was promoting. For example, it gave me “top foods by color.” The one Lean Cuisine pasta I’d inputted (fictional, and only added once) was my top “green” choice. A niçoise salad didn’t make the green list. A frozen pizza was red, but spaghetti squash and homemade turkey meatball lunch also landed in the “red” list (for the meatballs). If I didn’t know better, that would make the Lean Cuisine and frozen pizza seem like a better option than (or at least on par with) salad, squash, and homemade lean meats.
And let’s be real: although the app’s tagline is “Stop dieting. Get lifelong results,” this is definitely a diet—a diet based on restricting calories, no less. There’s nothing inherently wrong with this—and based on Noom’s approach, it could still help promote healthy behavior—but it’s good to know what you’re getting into.
Another Diet App Worth Considering
- 4.7-star rating on iOS, 4.2-star rating on Google Play
- Can sign up for “plans” for nutrition education and fitness classes
- Can customize your daily calorie goals
- Minimal education
- Low default calorie recommendation
MyFitnessPal is a tried-and-true diet app with a lot going for it—namely its specialized plans, many of which are built by registered dietitians. You can also seek out some nutrition education on the app (though it’s not as easy to access as some other apps). It encourages you to pick your “plan,” like low carb, macros, or high protein, right from the jump. This may be a plus or minus for you, depending on your goals.
I didn’t love its low starting calorie window. After inputting a 15-pound weight loss goal, it set me on a 1,220-calories-a-day track. (I’m 5’3”, for reference.) Calories automatically adjust upward for added exercise, which the app syncs from Apple Health. And the app provides workout routines, which you can also log. Regardless, trying to maintain a calorie count this low would leave most people (including our tester) feeling sluggish.
The app has several useful features, including a large database of foods that you can log and an easy-to-use platform. It’s not much more than a food diary, but it’s solid for that purpose. One feature I especially liked is that the premium version makes it easy to look at your carb/protein/fat breakdown, and it also highlights when a food is high in a certain element, like vitamin C or fiber, or flag when you’re approaching your recommended saturated fat or sodium limit for the day.
Who Should Try Diet Apps?
Being overweight or obese carries National Institute of Diabetes and Digestive and Kidney Disease “Health Risks of Overweight & Obesity” View Source , such as Type 2 diabetes, heart disease, high blood pressure, stroke, metabolic syndrome, and more. If you’ve been told by a medical professional that losing weight will be beneficial for your health, a diet app could be a helpful way to get started.
If you have a healthy relationship with your body and food but could use feedback on portion size or help tracking what you’re eating, these apps may be an option. Or if you’ve used calorie restriction in the past without harm, these apps can help you keep track without doing mental math.
Just be super aware of whether they start to promote restrictive habits—like anxiety if you can’t choose your own meals, skipping social events to avoid eating, and avoiding restaurants—in your food choices.
We recommend that anyone with a history or risk of disordered eating avoid diet apps. We also recommend consulting with a physician or registered dietitian before using a diet app, especially if you have a health condition like diabetes that may benefit more from an app or device specifically tailored to your condition.
Are Diet Apps Healthy?
Despite how “new” diet apps might feel, researchers actually have had some time to evaluate their efficacy. A randomized control trial had PubMed.gov “Comparing Self-Monitoring Strategies for Weight Loss in a Smartphone App: Randomized Controlled Trial” View Source and found it could help people lose “clinically significant” weight in the short-term (usually defined as a 5% reduction in weight over the course of six to 12 months). A much larger study of 35,921 Noom app users found that Scientific Reports “Successful weight reduction and maintenance by using a smartphone application in those with overweight and obesity” View Source , with just under a quarter of all users (22.7%) losing more than 10% of their starting weight. But a systematic review found that multi-component approaches, which involved an app but weren’t exclusively relying on them, had PubMed.gov “Efficacy of interventions that use apps to improve diet, physical activity and sedentary behaviour: a systematic review” View Source .
It’s worth noting that these studies tend to focus on weight loss, not overall health. Weight loss might be one reason to change your diet or exercise routines, but it’s certainly not the only one.
You may benefit more from integrating different kinds of foods into your everyday eating routine, rather than simply trying to eat less. Diets rich in fruits, vegetables, grains, seeds, legumes, and nuts (and low in fatty and processed meats) PubMed Central “Defining a Healthy Diet: Evidence for the Role of Contemporary Dietary Patterns in Health and Disease” View Source , including cardiovascular disease, cancer, diabetes, and cognitive impairment. And one recent study suggests that iScience “Obesity treatment: Weight loss versus increasing fitness and physical activity for reducing health risks” View Source .
The second thing worth noting is that most research only follows dieters for a few months. While many diets trigger weight loss in the short term, about 80% of dieters The American Journal of Clinical Nutrition “Long-term weight loss maintenance” View Source —and more have regained weight within five years. Other studies show that dieters who keep weight off for American Journal of Clinical Nutrition “Long-term weight loss maintenance” View Source increase their chances of longer-term success.
All this is to say: Whether these apps lead to sustained weight loss is unclear. Either way, your best best is to focus on building healthy habits, like eating more vegetables and getting more exercise, to help promote health in the long run.
Will A Diet App Help Me Lose Weight?
The apps we tested had two main methods of creating weight loss or weight maintenance. Most use “calories in, calories out” (CICO), and one, WW, uses a “points” system. Here’s what we know about those methods.
Does Calories In Calories Out (CICO) Work for Weight Loss?
American Journal of Physiology ““Calories in, calories out” and macronutrient intake: the hope, hype, and science of calories” View Source that the balance of how many calories you eat (calories in) versus how many calories you burn through activity (calories out) can play a role in body size, regardless of whether that calorie came from cake or spinach.
Diets that use CICO are trying to create a calorie deficit (eating fewer calories than you use in a day) for weight loss. They might also aim for maintenance calories (eating roughly the same amount of calories you use in a day) to maintain weight. Some people who are trying to gain weight, such as body builders, might also increase the number of calories they’re eating in order to achieve that goal. Weight gain was not a default option on any of the apps we tested, though through some manual adjustment, you could use them for that purpose.
But calorie counting doesn’t create the same results for everybody, and emerging research shows that there are several other factors that can impact weight that go beyond calories. These include things like Wiley Online Library “Metabolic adaptation delays time to reach weight loss goals” View Source , PubMed Central “Insufficient sleep undermines dietary efforts to reduce adiposity” View Source , Biological Psychiatry “Daily Stressors, Past Depression, and Metabolic Responses to High-Fat Meals: A Novel Path to Obesity” View Source , University of Rochester Medical Center “When Your Weight Gain Is Caused by Medicine” View Source , PubMed Central “Socioeconomics of Obesity” View Source , and PubMed Central “The Role of Exercise and Physical Activity in Weight Loss and Maintenance” View Source , among other factors.
Not to mention, accurately calculating calories in foods is remarkably challenging—and there’s a good chance our food labels aren’t capturing the whole picture. (We even ran into this during our testing, where apps would assign different calorie counts for the same food.)
What you eat does have an impact on your health, regardless of whether it affects your weight. The problem is that CICO could, in theory, allow someone to subsist on a diet of, say, popcorn, Diet Coke, and sugar-free Jello. This might allow for “successful” weight loss, but certainly doesn’t provide all the nutrients one needs. On the other hand, if someone uses CICO to fill their plate with nutrient-rich foods, it can be healthy.
CICO Evidence Test Rating: Healthy-ish
This method can be effective if you’re looking to lose weight, but long-term use may not be beneficial for everyone. CICO on its own also doesn’t promote healthy behaviors such as increasing plant-based foods or regularly getting physical activity.
Used by: Noom, MyFitnessPal, Lose It!
Does the Points System Work for Weight Loss?
In some ways, the Points system is similar to Calories In Calories Out—it’s still trying to create a calorie deficit to achieve weight loss or hit a baseline for weight maintenance. But the points system, which assigns dieters a set number of points to hit each day, is also trying to encourage certain choices over others. For example, foods with saturated fat and sugar cost more points, where foods with protein, fiber, and unsaturated fat cost fewer points. One randomized study suggests that using WW creates more weight loss than trying to figure out weight reduction on your own, but whether it works better than other CICO methods is unclear.
“Points” System Evidence Test Rating: Healthy-ish
This can be effective if you’re looking to lose weight, but it may not be sustainable for long-term use—especially because it ties you to a platform that uses the points system.
Used by: WW
What to Watch Out for in Diet Apps (And Diets)
When shopping for diet apps, keep your eyes peeled for these red flags.
Red flag #1: It recommends super low calorie intake.
“[You] should not go below 1200 calories per day unless that’s medically supervised—and even 1200 is very low for a sustainable lifestyle,” says registered dietitian Samantha Cassetty. “You want to make sure that you’re eating enough to support your energy and activities and also that it’s a sustainable amount—that you feel fueled throughout the day versus hungry, tired, sluggish, lethargic.”
Red flag #2: It promises unrealistic speed.
Slow and steady is the healthiest way to lose weight. That’s about CDC “Losing Weight” View Source . Any app that claims to deliver more than this veers into Penn Medicine “Want To Lose Weight Quickly? Here Are 7 Reasons Why Crash Diets Probably Won’t Work” View Source territory and likely won’t be sustainable (or good for you).
Red flag #3: It encourages you to purchase a lot of packaged, processed, “skinny” foods.
“The healthiest diets are predominantly whole foods or minimally processed foods,” Cassetty says. “There’s just mountains of evidence that show us that that’s the healthiest way to eat for a variety of reasons. It will help you manage hunger better, it will provide you with a spectrum of nutrients that your body needs to perform at peak function, to benefit your health, and prevent from any long term health problems.”
Red flag #4: It wants you to cut out whole food groups.
Also be wary of diet apps that recommend eliminating a food group, like carbohydrates, beans, wheat, fruit, or the like. “Any time that they’re restricting a food group is a red flag,” Cassetty says. Occasionally, individuals might benefit from restricting a certain food group, but it always runs the risk of causing “over-obsessing about foods, over-restricting foods, [and] being anxious about foods.” (And if you do have a food intolerance or allergy, it’s best to discuss with your physician, not an AI.)
Red flag #5: You don’t receive any feedback.
Apps should also provide more than a menu list or calorie counter—behavioral guidance is important, Cassetty says. “What to eat is a great part of the equation. But there’s also why people eat and that needs to be addressed, or else you’re not really going to develop healthy habits in the long term.” That’s true whether your intention is to change your weight or maintain it.
Apps should also be flexible to your lifestyle. This includes leaving room for the foods you genuinely enjoy, Cassetty says, as well as any health conditions you have.
Diet Apps and Eating Disorders
Another big thing to consider is the link between tracking food and disordered eating. 9% of Americans develop an eating disorder in their lifetime, and one study found that MyFitnessPal was being PubMed Central “My Fitness Pal Calorie Tracker Usage in the Eating Disorders” View Source . In the study, participants reported it contributed to their symptoms.
Every app we tested asked if we had an active eating disorder before using it, but did not ask about previous eating disorders. All it took was the click of a button to say “no” and move to the next screen. Not all eating disorders are detected—they’re particularly underdiagnosed and underscreened in communities of color—so just asking someone to disclose it doesn’t fully mitigate risk.
How We Got Here
Meet Your Guinea Pig
I’m Colleen Stinchcombe, a health writer based near Seattle, WA. I’ve been bamboozled by enough “lifestyle changes” to smell a restrictive diet a mile away.
Our Testing Process
We tested all four apps over the same one-week window. The first two days, we inputted the same “goal” and what we actually ate. Then we experimented with fictional food diaries that were heavy on processed takeout or prepackaged foods as well as home cooked whole foods to see if the apps could spot the difference and provide any feedback. (Womp womp, they didn’t.) We also tested inputting over and under calories to see how the apps responded. Then, we synced the apps with our Apple Health step counter to log exercise and see how it altered calorie windows.
The Diet App Buying Guide
Which Features Matter Most When Selecting a Diet App?
- Ease of use and ability to customize to your needs. If you’re not feeling satisfied with the number of calories you’re allotted each day, you should be able to change it. And it should be easy to use the app.
- Accurate nutritional education. There’s enough weight loss BS out there to fill the ocean twice over—nutritional education should preferably come from registered dietitians, or at the very least be backed up by the most recent research from major health authorities like the Centers for Disease Control and Prevention (CDC).
- Efficacy. Does the app do what it says it will do?
Diet Apps You Can Skip
WW / WeightWatchers
- 4.8-star rating on iOS, 4.6-star rating on Google Play
- Well-studied program that research suggests works for short-term weight loss
- Large database of food nutritional value, especially chain restaurants
- Calculating points for non-listed foods is near impossible
- Food database seems to favor processed foods
- Tough to customize your Points
The main reason WW (formerly known as Weight Watchers) fell short of the top spot is that you seem to need to quickly learn to speak WW code. It has educational tools, but it’s in a separate tab and mostly about teaching you about WW points rather than nutrition itself.
A cornerstone of WW’s program is “ZeroPoints” foods. Most of these foods are fruits and vegetables (though some fruits and vegetables, like avocado, do have points) and proteins like eggs, turkey, and tuna. On the one hand, this might encourage you to eat lots of plant-based foods and lean proteins. On the other hand, it feels like you’d be more apt to try to “trick” the system based on points—meanwhile not being within spitting distance of your intended calorie window.
Speaking of which, it’s kind of a nightmare trying to add home cooked meals to the WW app. (Much more so than other apps.) It’s got a healthy database of chain restaurant menus and packaged meals, but if you try to find “sautéed bell pepper,” for example, you’re SOL. For example, I went to add a cup of tea with soy milk (roughly 20 calories) which the app didn’t have. When I went to add it manually, it made me calculate the points—sans any guidance on how to do that.
- 4.8-star rating on iOS, 4.5-star rating on Google Play
- Can be used to track calories
- Offered dangerously low calorie plans
- Long questionnaire doesn’t seem to change much about the app
Lose It! “recommended” a plan with a somewhat reasonable calorie goal (1,500 calories per day). But the biggest reason this app didn’t get a recommendation is that it also gave the option of choosing other plans, including a “vigorous” plan that set a calorie goal at 1,000 calories per day—well below what is considered safe for an adult. As part of testing, I also put in a calorie count that was way lower than what it’s supposed to be, and the app didn’t register it as a blip.
Beyond that, the app performed similarly to MyFitnessPal, though it offered even fewer educational opportunities beyond a feed of articles that weren’t organized in any particular way. Like Noom, it asked a lot of personal questions upon sign up that didn’t seem to affect customization of the app.
If you think you or someone you know may be struggling with an eating disorder, we encourage you to pursue ANAD’s resources for help and information. You can also reach out to a volunteer at The National Eating Disorders Association for support, resources, treatment options, or other information you need through their chat, call, and text helplines. If you are in a crisis and need help immediately, text “NEDA” to 741741 to be connected with a trained volunteer at Crisis Text Line.
Our research and review process is intended for informational purposes only—never as a substitute for medical treatment, diagnosis, or advice. Recommendations or information found on this site do not infer a doctor-patient relationship. Always consult a healthcare provider if you have questions about how a product, service, or intervention may impact your individual physical or mental health. Our evaluations of products, services, and interventions have not been reviewed by the Food and Drug Administration. Information and research about health changes frequently. Therefore, some details or advice on this site may not be up-to-date with current recommendations. The Nessie is an independent publication and is not in any way affiliated with the production or creation of products, providers, services, or interventions featured in reviews or articles on the site.