Bangkok, Thailand (CNN) It's 6 a.m. on a Monday morning, and Bangkok is just starting to wake up. Street food vendors begin to serve breakfast as the streets, and sidewalks fill with morning commuters.

Behind the gates of Wat Yannawa temple, barefoot monks emerge, their saffron robes a pop of color in the early morning light. From the youngest to the oldest, they do this same routine every day: collect alms, or offerings, from the Buddhist faithful.

In metal pails that sway near their hips as they walk, they collect food, drinks and the occasional cash donation for the temple. They pray with the person who offers it, and then return home to prepare the meal with what they've been given.

More than 90% of Thailand's population follows Buddhism and the monks here are held in high regard, but there is growing concern about their health: Thailand's monks are gaining too much weight.

Restrictive diet

Thailand's National Health Commission Office says there are nearly 349,000 monks in Thailand, and almost half are considered overweight or obese.

There are several factors, but it largely centers around the morning routine -- and the changing nature of the offerings placed into the monk's pails.

The monks aren't able to control their own diet -- it's at the mercy of the offerings they receive each morning. Traditionally, those alms are calorie-rich foods, either processed or homemade -- with the Buddhist faithful wanting to offer something of high value and taste.

The monks are also forbidden from eating anything after 12 p.m., having only one or two meals a day between the hours of 6 a.m. and noon.

This means it's hard for monks to change their diet.

Professor Jongjit Angkatavanich, a pharmacist, dietician, and nutritionist who has been studying the health of Thailand's monks for the past eight years, describes the situation as a "ticking time bomb."

"When we look at the obesity rate, it's kind of like the first landmark that we used as an indicator," Jongjit said.

The monks are experiencing conditions such as diabetes, high blood pressure, eye issues and osteoarthritis in knees, but they know very little about them.

For example, one of the most shocking things Jongjit has seen is monks with amputated toes and feet because of diabetes, but the monks had no knowledge of the condition -- many had never even heard of diabetes.

Some 48% of Thailand's monks are overweight compared with 39% of the Thail male population.

A taste for soda

Obesity rates among Thailand's monks are higher than the wider population -- 48% of them are obese compared to 39% of the Thai male population, according to Jongjit's research. While people might think the monks are simply eating more, Jongjit said that isn't the case. The monks consume 150 less calories than Thai men.

So what's happening to Thailand's monks?

"After midday, they have to rely on a drink or beverage," Jongjit explained. "It has changed over time, from the ancient time -- right now, it is a soda, a soft drink, a sweetened beverage."

What's more, she said, is the monks often consume the sugary drinks on an empty stomach. "The sugar in the liquid is absorbed faster," she said. "It means the effect or consequence of the added sugar is even worse for a monk."

To complicate matters even further, the monks aren't supposed to exercise -- it's considered vain. Navigating those restrictions is an important part of the long-term solution.

Somdet Phra Mahathirajarn is the Abbot of Yannawa temple -- its highest-ranking monk. He's been leading the charge in implementing changes suggested by Jongjit and her team, including finding a way around the exercise restrictions and healthier menu options for the novice monks' midday meal, as the novices get one meal prepared by the temple before noon in addition to the morning alms.

A young monk gets his health checked.

"We consider their intention" when it comes to exercise, he said, allowing exceptions for health reasons. "My department has to coordinate with the government to dispatch mobile medical units to educate the monks, so they can learn about proper exercise, proper rest and proper living."

Keeping track

One of the mobile medical units arrived later that day. A fleet of health workers armed with scales and blood pressure cuffs descended on Yannawa temple, measuring and tracking the health of the youngest novice monks. From blood sugar levels to weight and body mass index, the numbers are recorded and entered into a database -- no small task, considering the sheer number of temples and monks in Bangkok alone.

Yannawa Temple in Bangkok.

"We started this health check-up for the monks in temples all over Thailand, and especially in Bangkok," said Dr. Somchai Teetipsatit, director of the Health Promotion Division for the Bangkok Metropolitan Administration. "We have 454 temples in Bangkok, with about 16,000 monks."

To cover everyone, both public and private healthcare clinics are involved, spurred on by a unique health charter implemented by the government and the National Health Commission Office in 2017. The goal is to teach not only the monks, but the public, about proper nutrition, so they can take care of each other.

Phupha Srichalerm is a 17-year-old novice monk from a province in southern Thailand. He's been studying at Yannawa temple for nearly five years, and now his Buddhist education also includes nutrition.

"It's good because it makes me aware about diet," he said. "I've changed my dietary habits." For starters, he's begun swapping out the sugary afternoon drinks in favor of water. Otherwise, he now understands that the risks of obesity and the diseases that come with it are serious.

A monk at Wat Yannawa in Bangkok, Thailand.

In the eight years since Jongjit first started this work, she has seen some progress.

"We started small," she said. "But we have to spread [the message]. Now we call it 'one temple, one hospital.' And with this national health strategy, we will distribute our [educational] media to at least 11,000 hospitals in Thailand -- from the main hospitals in the provinces to the primary care district hospitals, the roots of our community" -- going to the root of the community, to help the heart of the community.