London School of Hygiene & Tropical Medicine (LSHTM)

Helping GPs tackle childhood obesity more effectively

Screen showing London School of Hygiene & Tropical Medicine (LSHTM) website

At a glance

  • Tech Stack

  • Ruby on Rails
  • MySQL
  • JavaScript
  • Core Services

  • Discovery & Strategy Consulting
  • User Experience Design
  • Web App Development
  • Additional Services

  • Data Analytics & Business Intelligence
  • Data Protection & Accessibility Compliance
  • Fractional Product & Technical Leadership

Bit Zesty team provided us with the best tool possible. We are very thankful for their work on this and are really loving how the tool has turned out!

Aine Skow, CATCH Product Owner, London School of Hygiene and Tropical Medicine


The London School of Hygiene and Tropical Medicine (LSHTM) focuses on improving public health through conducting research and trials.

Childhood obesity is a growing public health concern, with over 30% of UK children classified as overweight or obese.

LSHTM were conducting a study named CATCH (Computer-Assisted Treatment of CHildren who are overweight) to see whether a digital tool could be developed to improve the diagnosis of obesity in children and the advice the child and the parent get when visiting their GP.


LSHTM approached Bit Zesty to build the CATCH tool. We began by developing a paper-based wireframe, which we tested with GPs and nurses. This allowed us to quickly pilot key concepts and to uncover new user needs.

We used the testers’ feedback to refine and iterate until we were ready to develop a working prototype.

We built a browser-based digital service that leads health practitioners through a series of questions to ask their patient. Based on the answers, the tool uses national clinical guidelines to:

  • calculate the child’s BMI
  • produce a risk assessment based on the child’s social-demographic information
  • create a lifestyle assessment and personalised lifestyle advice, based on the above

As the tool was being developed for a research study, we made sure there was an easy-to-use administrator interface so the LSHTM team could customise and adjust the tool during their research study. For example, we made it easy for the team to refine the formulae and rules driving the tool’s calculations.


Once we had a prototype, we carried out user testing with healthcare professionals.

The user testing helped us to identify new functionality for the tool. For example, during testing, several health practitioners said they wanted to be able to print the lifestyle advice so they could give a copy to their patients.

Testing also allowed us to see how health practitioners actually used the tool. A key finding was that they often stopped following the tool’s sequence of questions part way through, to ask patients their own follow-up questions. In most cases, the same follow-up questions were covered later in the CATCH tool. This broke the flow and added time to the GP appointment. To prevent this, we added a simple start page that instantly informs GPs of what to expect. When we tested again, after this change was made, with the new set of health professionals, they no longer jumped ahead with the consultation.


Calculating a child’s BMI and making personalised recommendations can be difficult, particularly as it’s not something most health practitioners have to do regularly. The tool handles all the complexity for the user and is based on the latest best practice formulae and clinical guidelines.

Time was also an important consideration. On average GPs only have ten minutes per appointment, which may not be enough to manually calculate BMI, assess the patient’s lifestyle and make personalised recommendations. Our user testing helped us to develop a tool that was as quick and easy to use as possible.


LSHTM’s pilot study found that 86% of patients and 100% of the health practitioners involved were satisfied with the CATCH tool.

Health practitioners said the tool was useful, easy to use and saved time.

Talking about a child’s weight can be sensitive, but patients were more likely to see the results and recommendations from the tool as objective and non-judgemental. Although most parents had already been concerned about their child’s weight, several referred to the CATCH consultation as a “wake-up call” that alerted them to the severity of the problem.

Based on the results of the pilot study, LSHTM concluded that the tool was an effective way to assess and manage childhood obesity.