Teenagers who turn to artificial intelligence for weight loss advice are being handed dangerously restrictive meal plans that could severely impact their physical growth and development. According to a new study, popular AI chatbots consistently generate diet plans that miss key nutritional targets and underestimate daily energy requirements by the equivalent of an entire meal.
Published in the journal Frontiers in Nutrition, the research compared the meal-planning abilities of five free AI models — ChatGPT 4, Gemini 2.5 Pro, Bing Chat-5GPT, Claude 4.1, and Perplexity — against the expert recommendations of a registered dietitian specialising in adolescent diseases.
The researchers prompted the tools to create a three-day meal plan, including three meals and two snacks per day, for four hypothetical 15-year-olds falling into the overweight and obese percentiles.
“We show that diet plans generated by AI models tend to substantially underestimate total energy and key nutrient intake when compared to guideline-based plans prepared by a dietitian,” said Dr Ayşe Betül Bilen, an assistant professor at Istanbul Atlas University. “Following such unbalanced or overly restrictive meal plans during the teenage years may negatively affect growth, metabolic health, and eating behaviours.”
The missing meal
When the AI-generated plans were analysed, the clinical results were alarming. The AI models calculated the teenagers’ daily energy requirements to be almost 700 calories lower than the dietitian’s calculations. This massive deficit is equivalent to skipping a full meal and is large enough to trigger serious clinical consequences.
Furthermore, the AI completely skewed the necessary macronutrient balance. Instead of following clinical guidelines, the chatbots appeared to mimic popular adult diet trends, pushing high-protein and high-fat meals while significantly slashing carbohydrates.
The study revealed the following AI macronutrient deviations:
- Carbohydrates: Slashed by an average of 115g, making up only 32 to 36 per cent of the energy intake, which is far below the recommended 45 to 50 per cent.
- Lipids (Fats): Pushed to represent 41 to 45 per cent of energy intake, well above the 30 to 35 per cent clinical guideline.
- Protein: Increased by around 20g to make up 21 to 24 per cent of the diet, exceeding the recommended 15 to 20 per cent.
Dr Bilen pointed out the specific dangers of this approach: “AI-generated diet plans consistently deviated from the recommended macronutrient balance, which is particularly problematic for adolescents.”
Popularity over precision
Despite the availability of evidence-based guidelines from organisations such as the World Health Organisation, AI tools fail to reliably integrate age-specific nutritional requirements into their outputs.
“AI models are primarily trained to generate responses that appear plausible and user-friendly rather than clinically precise,” Dr Bilen explained. “Our findings suggest they may rely on generalised or popular diet patterns instead of fully integrating age-specific nutritional requirements.”
Because many teenagers lack access to professional dietitians, the researchers urge extreme caution when using AI for meal planning. While the technology can be a complementary educational aid, it should not replace professional dietary counselling, especially for vulnerable adolescents.
Dr Bilen concluded: “Adolescence is a critical period for physical growth, bone development, and cognitive maturation. Lower energy and carbohydrate intake, combined with increased protein and fat ratios, may pose risks during the adolescent growth period.”
