Can You Trust Image-Based AI Calorie Trackers?

Image-based AI calorie trackers are gaining popularity, promising to simplify the process of counting energy consumed. But do they offer more accurate calculations? We tried one of these apps, SnapCalorie.

Generative artificial intelligence (AI) is finding its way into healthcare and wellness – from interpreting radiology results to chatbots creating fitness plans.

Nutrition is no exception, with more and more people using AI-powered calorie trackers. One such image-based tool, Cal AI, recently made the headlines for generating over 5 million downloads in eight months.

However, it isn't the first-of-its-kind mobile application. SnapCalorie, an image-based calorie tracker created by a co-founder of Google Lens, was released back in 2023.

Tools that allow uploading a photo of a meal and learning about its calories and macronutrients within seconds may seem more convenient than traditional calorie trackers that rely on logging in individual ingredients.

But are these calorie trackers always accurate? I tried SnapCalorie to find it out.

How does SnapCalorie work?

Once you download SnapCalorie, it asks you to add your personal data, including your sex, weight, height, physical activity levels, and your goal – to reduce, maintain, or gain weight. Based on this data, the app suggests a daily calorie intake and the amounts of nutrients.

Being about 5.7 ft tall, weighing 127 lbs, and having moderate activity levels of three workouts per week, I set my goal to maintain weight.

The app recommended I consume 2,139 kcal per day, with the following macronutrient breakdown:

• 59 g of fat, constituting 25% of daily calories
• 160 g of protein, constituting 30% of daily calories
• 241 g of carbohydrates, constituting 45% of daily calories

According to Sandra Vigelienė, a WellnessPulse content researcher, the recommendations made by the app are mostly in line with the dietary guidelines, and the calorie intake suggestions are likely reasonable. This is because such apps usually calculate calorie needs using the same formulas as nutritionists.

For example, the Dietary Guidelines for Americans recommend that 45-65% of total calories should come from carbohydrates, 10-35% from protein, and 20-35% from fat.

However, Vigelienė says protein content suggestions align with high-protein diets and may not be necessary for most. Adults need about 0.8 g of protein per kg of body weight, whereas the app's recommendation of 2.8g/kg is more suitable for athletes or those who are highly physically active, especially those who practice strength training.

"If your goal is to simply support a healthy diet without changing your body composition or losing weight, such protein recommendations may not be necessary," she says.

Eating too much protein in the long term may cause digestive issues like bloating, constipation, and kidney damage, among other health risks for some people.

A meal can be logged in by taking a photo via the application. It takes several seconds to generate a food score, which evaluates a meal's healthiness, calorie count, and macronutrient breakdown.

The app lists every individual ingredient it can recognize, its estimated amount, and how many calories it contains.

Desirable characteristics like 'low sodium,' 'low sugar,' and 'high protein' are highlighted in green.

Is SnapCalorie free?

SnapCalorie has a free version that allows logging in three meals a day.

The Premium version, which costs €89.99 EUR a year, has a 7-day free trial. This version allows unlimited meals to be logged in and personalized tips from an AI nutritionist.

The science behind SnapCalorie app

According to the SnapCalorie website, the application relies on the Nutrition5k dataset, which contains visual and nutritional data of about 5,000 diverse real-world food dishes. The data includes 20,000 short videos generated from these meals.

The dishes are made from more than 250 different ingredients, with the most common ones including chicken, scrambled eggs, olives, cauliflower, among others.

Each dish has a full breakdown of ingredient labels, their quantities, and their macronutrient information computed using the USDA Food and Nutrient Database.

Is SnapCalorie accurate?

Using the free version of SnapCalorie, I tested the app on six meals and snacks. Here are some examples:

Egg avocado toast for breakfast

Quick avocado toast is my usual breakfast option, which consists of one smashed avocado mixed with a drop of extra virgin olive oil and a tiny pinch of salt, spread on two slices of white bread and eaten with one hard-boiled egg.

SnapCalorie assigned the meal a food score of 33, suggesting that it is on the less healthy side.

The app flagged the meal as 'high fat.' Such designation misses the nuance of the types of fat and their impact on health. An average avocado contains 22 g of fat, of which 19 g is 'the healthy' monounsaturated and polyunsaturated fats, the long-term consumption of which may support heart and overall health.

Moreover, the meal is considered 'low protein.' With about 6.3 g of protein in an egg and 3 g in avocado, the toast provides nearly 10 g of protein, which can meaningfully contribute to the recommended daily intake.

Banana as a snack

Bananas are one of my favorite options for calming down the sweet tooth. The Centers for Disease Control and Prevention (CDC) recommends whole fruits as a healthier alternative to sugary desserts.

However, SnapCalorie assigned the banana a score of 50, flagging it as 'high sugar.'

While a large banana may contain 17 g of sugars, they are natural and can be part of a balanced diet, especially because they are found in foods high in fiber, minerals, and vitamins.

Natural sugars shouldn't be confused with added sugars, which are added during the processing of foods and are abundant in sugary beverages and desserts. The American Heart Association (AHA) recommends that no more than 6% of daily calories come from added sugar, as their high consumption is associated with an increased risk of obesity and diabetes, among other conditions.

When I logged in a row of milk chocolate with hazelnuts, it was also designated as 'high sugar,' as it contains 12 g of sugar. If a larger context is not provided, chocolate may appear like a better option than a banana for those trying to reduce sugar intake, which it is not.

Chicken stir fry with rice for lunch

I thought that chicken stir-fry with red bell pepper, zucchini, garlic, and rice would be the least healthy meal of the day, but SnapCalorie gave it a score of 83, suggesting it is low in calories and fat but high in protein.

What caught my attention was the 'low sodium' designation, with an estimated 634 mg, likely because the app didn't include ingredients I used for marinating chicken, such as soy and teriyaki sauces.

Half a tablespoon of soy sauce contains 439 mg of sodium, and two spoons of teriyaki sauce has 1380 mg. This means the marinade alone nearly reaches the daily sodium intake of 2,300 recommended by the AHA. Consuming too much sodium can increase blood pressure and the risk of heart disease and stroke.

Tofu bowl with quinoa for dinner

For dinner, I decided to treat myself to a meal at a lovely vegan restaurant. I chose a tofu bowl with quinoa, avocado, spinach, edamame, cherry tomatoes, radish, carrot, and nuts.

The bowl earned a food score of 50 and was flagged as 'low fiber' despite being made entirely of plant-based ingredients, many of which are known for their high fiber content.

For example, half a cup of edamame provides about 2.6 g of fiber, half a cup of quinoa 2.5 g, and half an avocado contains about 5 g of fiber, contributing to about one-third of the recommended daily intake for women.

SnapCalorie's pros and cons

SnapCalorie did not always provide accurate measurements. However, here are the reasons why it's worth to give a try:

• Easy and quick to use. The meal analysis is available within seconds and there's no need to log in individual ingredients.
• Educational. Although the macronutrient breakdown may lack accuracy, it can be beneficial to individuals who are just starting their journey to learn more about nutrition.
• Even approximate calculations can help people better understand their energy consumption habits, especially when the app raises awareness about high-calorie but low-nutrient foods.
• Free. Its alternative, Cal AI, requires a subscription.
• An AI chatbot may help overcome existing disadvantages. When asked if sugar in bananas is bad for health, the chatbox explained the difference between natural and added sugars, highlighting the benefits of eating fruits.

At the same time, the app seems to have some serious cons:

• Some labels, such as 'high sugar' for fruits or 'low fiber' for plant-based meals, may lack nuance, potentially confusing users with less knowledge about nutrition.
• The app doesn't always recognize ingredients. For example, in a salad, chopped avocado was counted as chopped cucumber.
• It may not take into account 'invisible' ingredients, especially those used for cooking, like oils, sauces, and salt.
• The benefits of calorie counting for weight loss are questionable.

Melanie Crum, RD, says image-based calorie trackers can be helpful for those who want to save time or don't like logging food.

But sometimes, the app might guess wrong if the picture isn't clear or if there are a lot of foods on the plate or a lot of ingredients. So, it's cool and fun, but it's still good to double-check.

Melanie Crum, RD

Does calorie counting work?

'Calories in, calories out' is a widespread belief that creating a calorie deficit when you consume fewer calories than you burn leads to weight loss.

However, some experts say that such a model oversimplifies complex metabolic processes.

For example, metabolic rate – the number of calories we burn when resting – varies from person to person based on factors like body composition, and it changes when we alter our diet and lose weight.

Moreover, not all calories are equal, and they affect hormones, brain response, and energy expenditure differently.

There are also concerns about the link between calorie tracking and eating disorders. Evidence suggests that calorie counting is more common among those with disordered eating patterns, especially when used for weight loss rather than to improve health. Some users report that calorie trackers contribute to their eating disorders.

Crum says counting calories can help some people lose weight because it shows how much they eat, but sometimes it can feel stressful or confusing.

She says, "What matters most is eating healthy foods, like fruits, vegetables, lean meats, and whole grains, and paying attention to when you feel full. Moving your body and getting enough sleep also help."