The road to healthier eating and weight loss is paved with difficulties, from burgers and cookies in the school cafeteria to calorie-packed beers at your favorite bar, but there's a smartphone app that wants to help.

Kurbo Health, a startup with a subscription app primarily meant for children, is becoming quite popular among adults as well. Based on behavior modification methods designed at Stanford, the food-tracking app helps reduce body mass index (BMI) over time.

The system works via traffic light psychology -- calorie-packed foods are red, foods that are OK in moderation are yellow, and the health nut's dream foods are green.

The app was designed for kids, urging them to create daily logs of their food items and portions. It budgets the amount of red-light foods they can eat each day and keeps their parents informed of their active use of the app. It does not, however, tell parents exactly what their kids eat, which may be a relief to young users.

Co-founder Joanna Strober designed the app while helping her son lose weight. A doctor's visit made her realize what they were lacking -- a reliable tool her son could use daily to track his diet, warn him about calorie-packed foods and keep her in the loop. Looking at Stanford's childhood obesity program, which has helped hundreds but is too expensive to be readily accessible, Strober found the inspiration she needed. Seeing that the app community only had reliable programs for people 18 and older, she created an accessible, $10/month app for kids.

The app also offers expert coaching and support, with reminder notifications to use the app more and congratulatory messages when users keep to their red budget. The whole family gets the app with that price tag, allowing for a support system outside the smartphone.

So far, the program is proving to be effective in its simplicity and elegant design. Beta user Tiana Lepera, 14, explains how regular usage of the app gets her to form healthy habits.

"Even when we go to restaurants, we know that certain foods would be red lights, yellow lights and green lights. If I don't eat the bread that will be one less red light. You always think about it. It changes the way you're thinking about food." Lepera has lost 10 pounds since beginning the program.

The app's appeal isn't limited to kids. Lepera's mother has lost 29 pounds while using the program. While initially designed for kids, the program is based on a simple principle: People, young and old, are bad at calorie counting. Color-logging? Not so much. Users of all ages can benefit from the app's beautiful simplicity.