Diet apps are smarter than ever – but do they actually work?

Trigger warning: This article discusses weight loss apps, which may be triggering for people at risk of disordered eating.

Diet apps used to count calories and steps. Now, many of them come with AI coaching and meal planning, alongside tools for tracking nutrients and weight-loss medication. But does this actually make them more useful than their older incarnations, or just more all-consuming?

Here's the evidence on their effectiveness, how to choose the right one, and when they can do more harm than good.

"Research suggests food and nutrition apps can help people make healthier food choices, especially when they include proven behaviour-change strategies like tracking progress, setting goals, and receiving feedback," says Dr Rosalind Fallaize, registered dietitian and professor of dietetics at the University of Hertfordshire.

"But not all apps are equal, and their effectiveness depends on many factors including the quality of the app, whether the advice is evidence-based, and how regularly people use it."

To be clear, when we talk about 'diet apps', we're actually referring to a broad range of products. The three main types are:

These all work in different ways and studies tend to focus on individual types. Just because one study found one type of app to be potentially effective, it doesn't mean all diet apps are useful to all people.

"Some studies find that app-based interventions produce modest short-term improvements in weight and eating behaviours, particularly among people who engage with them consistently," says dietitian and author, Nichola Ludlam-Raine.

One particular large-scale study, external looked at data collected by one of the best-selling apps over 18 months. In that study, 78% of users reported a decrease in body weight when they used the app for an average of nine months.

But this was self-reported, observational data, and the people who tend to choose these apps are tech-savvy and already motivated to make changes. All this means the data might appear more positive than if collected from a wider sample with controlled variables.

Plus, points out Ludlam-Raine, "Engagement often declines over time, and the benefits appear smaller and less certain in the longer term."

Even if people do stick with them and use them consistently, some apps will be better than others.

"No diet app is 100% accurate," points out dietitian, performance nutritionist and author, Dr Lina Patel. "Food databases are based on estimates and extrapolated data, not precise measurements."

A recent study, external even highlighted that the quality of data some apps use can lead to bias. For example, if the data lacks diversity, the advice could be 'less relevant for certain populations.'

"The biggest shift is from passive logging to active support," says Dr Hans Johnson, a medical doctor and clinical lecturer in applied artificial intelligence at the University of Bristol.

Johnson, who is also research lead for weight-loss app, Voy, has studied the effectiveness of these apps.

"Five years ago a diet app was essentially a digital notebook: you typed in what you ate and it gave you a [calorie] number.

"AI has changed that fundamentally. The technology has moved from counting to coaching."

This means many apps are now geared toward helping people change behaviours and build healthy habits they can stick with, whether that's eating balanced meals, moving more often or supporting medical treatments like GLP-1s.

"GLP-1 medication is often prescribed without the wraparound support needed to make it successful in the long term," says Patel.

"The medication reduces appetite, but it doesn't teach someone how to nourish themselves, preserve muscle mass or build healthy habits.

"Digital services, increasingly powered by AI, can certainly help bridge that gap."

Indeed, experts say there's a growing interest in the nutritional quality of food, as opposed to just the number of calories it contains.

"We studied nearly 58,000 people, external in the UK taking GLP-1 medications through the Voy platform," says Johnson.

"Patients who engaged with the digital side of the programme, attending nutrition education and tracking their weight using the app, lost significantly more weight than those who took the medication without engaging."

He says that at three months, engaged patients had lost over 50% more weight than non-engaged patients, concluding that weight-loss drugs work best alongside wider support.

While the above research is industry-backed, other independent studies have drawn similar conclusions, external.

"For some people, particularly those with a history of disordered eating or an unhealthy relationship with food, constant monitoring can reinforce perfectionism and rigid food rules," says Patel.

"Obsession can gradually become restriction, and restriction can develop into disordered eating."

A 2024 study of young adults, external found that using self-monitoring apps for weight management specifically was associated with increased disordered weight-control behaviours over time.

"This is something the industry needs to be honest about," warns Johnson.

"For [some] people, the healthiest choice is not to track at all, and a responsible service should help them recognise that."

If an app makes you feel stressed, guilty or overwhelmed, it's probably not the right one for you.

1. Is the advice given or reviewed by qualified health professionals?

2. Are its goals realistic and flexible?

3. Can I use it without counting every calorie?

4. Can I turn off weight and calorie notifications?

5. Does it explain why it is making recommendations?

6. How will it use and share my health data?

7. Does using it make me feel supported rather than guilty or anxious?

The app with the most features won't necessarily be the most helpful. Think about overall health and wellbeing as opposed to something as specific as weight.

If you have an underlying health condition or a history of disordered eating, speak to a GP rather than downloading a diet app.

What actually matters is whether the advice is credible, the tools suit you and your routine, and the interactions support your health rather than dominating it.

"Alongside any digital tool, it's important to develop your own interoception – the ability to tune into your body's signals of hunger, fullness, energy and satisfaction," says Patel.

"Ultimately, technology should help you reconnect with your body, not disconnect you from it."

If you are concerned or have been affected by disordered eating, help and support is available.

Originally published July 2019. Updated July 2026.

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