A Gram Research analysis of 2,861 Vietnamese teenagers found that over 80% eat prepared foods from restaurants or vendors daily, contributing 22-26% of their daily calories. While these foods provide adequate vitamins and minerals, they contain more unhealthy fats and salt and fewer vegetables and whole grains than home-cooked meals, resulting in lower overall diet quality despite higher calorie intake.
A new study of nearly 2,900 Vietnamese teenagers found that over 80% eat prepared foods from restaurants or street vendors daily. While these foods provide important nutrients and energy, they tend to be higher in unhealthy fats and salt, and lower in nutritious food groups like vegetables and whole grains. According to Gram Research analysis, teens who eat more prepared foods outside the home consume more calories overall and have less healthy diets, even though they get adequate vitamins and minerals. The research suggests that making food environments healthier—through better labeling, reducing salt and sugar in prepared foods, and promoting nutritious options—could help teenagers make better eating choices.
Key Statistics
A 2026 cross-sectional study of 2,861 Vietnamese adolescents ages 11-19 found that over 80% consumed prepared foods from outside the home on the previous day, contributing 22-26% of their total daily energy intake.
According to research reviewed by Gram, prepared foods outside the home contained significantly higher amounts of total fat, saturated fat, and sodium compared to home-prepared foods, while being lower in vegetables and whole grains.
A 2026 study of nearly 2,900 Vietnamese teenagers found that those consuming more prepared foods outside the home had higher micronutrient adequacy but lower overall diet quality scores compared to those eating primarily home-cooked meals.
Research from 2,861 Vietnamese adolescents showed that smartphone ownership, pocket money, female sex, and higher socioeconomic status were significantly associated with greater consumption of prepared foods outside the home.
The Quick Take
- What they studied: How much prepared food teenagers eat when they’re away from home, and whether it affects the quality of their overall diet
- Who participated: 2,861 teenagers ages 11-19 from rural, suburban, and city areas in Vietnam. Researchers asked them what they ate in the previous 24 hours
- Key finding: More than 8 out of 10 teens ate prepared foods outside the home, which made up about one-quarter of their daily calories. These foods were higher in unhealthy fats and salt but lower in vegetables and whole grains
- What it means for you: If you’re a teenager who eats out frequently, you’re getting enough calories and some nutrients, but you might be missing out on healthier food groups. Choosing better options when eating away from home could improve your diet quality
The Research Details
Researchers surveyed 2,861 teenagers in Vietnam across three different types of areas: rural villages, suburban towns, and cities. They asked each teen to describe everything they ate and drank in the 24 hours before the survey. The researchers then analyzed which foods came from restaurants, street vendors, or other places outside the home (called ‘prepared out of home’ or POH foods) versus foods made at home.
To measure diet quality, they used a scoring system called the Global Diet Quality Score, which rates how healthy a diet is based on the types of foods eaten. They also calculated how many vitamins and minerals the teens were getting. The researchers looked at differences between boys and girls, rich and poor families, and teens in different locations.
This type of study is called cross-sectional, meaning researchers took a snapshot of what teenagers were eating at one point in time, rather than following them over months or years.
Understanding what teenagers eat away from home is important because eating habits formed in adolescence often continue into adulthood. By identifying which teens eat the most prepared foods and why, researchers can design better strategies to improve food environments and help young people make healthier choices
This study is reliable because it included a large number of teenagers (2,861) from different types of communities, making the findings more representative. The researchers used a detailed 24-hour recall method, which is considered a gold standard for measuring what people eat. However, because it’s a snapshot study rather than following teens over time, we can’t be certain that eating prepared foods directly causes less healthy diets—other factors might be involved. The study was conducted in Vietnam, so results may differ in other countries with different food environments
What the Results Show
The most striking finding was that over 80% of Vietnamese teenagers ate prepared foods from outside the home on the day they were surveyed. These foods contributed between 22-26% of their total daily calories—roughly one-quarter of what they ate.
When researchers looked at the nutritional quality, they found that prepared foods outside the home had both good and bad characteristics. The bad news: these foods contained more total fat, saturated fat (the unhealthy kind), and sodium (salt) compared to foods made at home. The good news: prepared foods actually had higher concentrations of vitamins and minerals per serving.
Teenagers who ate more prepared foods consumed more total calories each day and got adequate amounts of most vitamins and minerals. However, their overall diet quality scores were lower because prepared foods were missing important food groups like vegetables, fruits, and whole grains. These healthy foods were underrepresented in the prepared foods available to teenagers.
The study found important differences based on where teenagers lived and their family’s income. Teenagers from wealthier families, girls more than boys, and teens who had pocket money or owned smartphones were more likely to eat prepared foods outside the home. These patterns were different in rural areas compared to cities, suggesting that food environments and access to money shape eating habits differently depending on location.
This research aligns with previous studies showing that eating away from home is associated with higher calorie intake and less healthy diets in many countries. However, this is one of the first detailed studies examining this pattern in Vietnamese adolescents specifically. The finding that prepared foods have higher micronutrient density is interesting and suggests that the quality of prepared foods varies—some are more nutritious than others, depending on what’s being served
The study only captured what teenagers ate on one day, so it doesn’t show whether these eating patterns are consistent over time. Teenagers might have reported their food intake inaccurately from memory. The research was conducted only in Vietnam, so findings may not apply to teenagers in other countries with different food systems. The study shows associations (which factors go together) but cannot prove that eating prepared foods directly causes less healthy diets—other unmeasured factors could be involved
The Bottom Line
If you’re a teenager, try to balance eating prepared foods with home-cooked meals that include more vegetables and whole grains. When choosing prepared foods, look for options lower in salt and unhealthy fats. Parents and policymakers should support healthier food environments by encouraging restaurants and vendors to offer more nutritious options and by using warning labels on unhealthy foods. Confidence level: Moderate to High—this is based on a large study, though more research over time would strengthen these recommendations
Teenagers and their parents should care about these findings, especially if eating out is a regular habit. Policymakers, school administrators, and food vendors should use this research to create healthier food environments. Healthcare providers can use this information when counseling teenagers about nutrition. This research is less relevant for people in countries with very different food systems than Vietnam
If a teenager starts choosing healthier prepared foods or eating more home-cooked meals, they might notice improved energy levels and digestion within 2-4 weeks. Longer-term benefits like better weight management and disease prevention typically take 3-6 months to become apparent
Frequently Asked Questions
Is eating prepared food from restaurants bad for teenagers?
Prepared foods aren’t inherently bad—they provide calories and nutrients—but they tend to be higher in unhealthy fats and salt while lower in vegetables and whole grains. A 2026 study of 2,861 Vietnamese teens found those eating more prepared foods had lower diet quality overall, even with adequate vitamins and minerals.
How much of a teenager’s diet should come from eating out?
The research suggests prepared foods currently make up 22-26% of teenagers’ daily calories. Limiting prepared foods to one meal per day or less, while ensuring home-cooked meals include vegetables and whole grains, appears to support better overall diet quality.
What makes prepared foods less healthy than home-cooked meals?
Prepared foods outside the home typically contain more salt, unhealthy fats, and sugar while including fewer vegetables, fruits, and whole grains. These missing food groups are important for long-term health, even when prepared foods provide adequate vitamins and minerals.
Do all teenagers eat prepared foods equally?
No. A 2026 study found that girls, wealthier teens, and those with pocket money or smartphones ate more prepared foods. Patterns differed between rural and urban areas, suggesting location and access to money influence eating habits differently.
Can eating prepared foods affect a teenager’s weight?
The research shows teenagers eating more prepared foods consume more total calories daily. While this doesn’t guarantee weight gain, higher calorie intake combined with less healthy food groups may contribute to weight management challenges over time.
Want to Apply This Research?
- Log each meal eaten outside the home for one week, noting the restaurant or vendor, the food chosen, and whether it included vegetables or whole grains. Track your total daily calories and compare days when you eat more prepared foods versus home-cooked meals
- Set a goal to eat prepared foods for no more than one meal per day, and when you do eat out, choose options that include vegetables or whole grains. Use the app to find restaurants or vendors near you that offer healthier prepared meals
- Weekly check-ins: Count how many meals you ate outside the home, calculate the percentage of your daily calories from prepared foods, and rate your overall diet quality. Track this over 4-8 weeks to see if you can gradually shift toward more home-cooked meals while maintaining balanced nutrition
This research describes associations between eating prepared foods and diet quality in Vietnamese teenagers and should not be interpreted as medical advice. Individual nutritional needs vary based on age, activity level, health status, and other factors. Teenagers with specific dietary concerns, food allergies, or medical conditions should consult with a healthcare provider or registered dietitian before making significant changes to their eating habits. This study was conducted in Vietnam and findings may not directly apply to teenagers in other countries with different food systems and environments.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.