It is a remote Amazon strain that has been found to have the "healthiest hearts ever examined".
However, scientists now fear an increase in cases of heart disease and obesity in the Tsimane community in the lowlands of Bolivia.
Researchers say that the 6,000-person strain is becoming less isolated by improving road and river transport links.
And this affects their diet, as figures show that the tribe buys 300 percent more sugar and cooking oil than five years ago.
Researchers fear that the worldwide spread of Western diets leads to overweight, type 2 diabetes and heart disease rates in healthy communities.
The peasant gathering community Tsimane (pictured) from the lowlands of Bolivia once had the "healthiest hearts ever examined". However, their sugar and oil consumption is rising as a result of the improvement in road and river transport links that allow the western diet to spread worldwide
The tsimans have low rates of obesity and type 2 diabetes as well as healthy blood pressure and cholesterol levels.
Researchers from the University of California, Santa Barbara, asked 1,299 Tsimane adults to fill out questionnaires for food.
They were asked to recall several times between 2010 and 2015 what they had eaten the previous day.
"Our previous work has shown that the Tsimans have the healthiest hearts ever examined," said senior author, Professor Michael Gurven.
"Of course there is a great interest in understanding why and how."
At the beginning of the study, the tsimane diet was high in calories, consuming between 2,422 and 2,736 a day.
More than 60 percent of these calories come from carbohydrates, consuming between 376 and 423 grams per day – mainly from plantain and rice.
The remainder of their diet, which consisted largely of fish and game, consisted of 119 to 139 grams of protein and between 40 and 46 grams of fat.
Despite their caloric diet, they maintained their health, with nine out of ten clear arteries.
The researchers, led by Thomas Kraft, also said that the older Tsimane people even had the blood vessels of the 50-year-olds.
It is believed that their active lifestyle keeps them so healthy that an average adult takes 17,000 steps a day compared to 5,100 Americans.
It turned out that the people in Tsimane bred or fed most of their food, and only bought eight percent of it on the markets.
However, despite their simple diet, they had much more healthy nutrients such as potassium, magnesium and selenium than the Americans.
Their dietary fiber intake was also almost twice that of a US resident. However, they lacked calcium and vitamins D, E and K.
"They are physically active – not by routine exercise, but by using their bodies to feed their fields and the forest," said Professor Michael Gurven, lead author of the study.
"You can not see what you eat, regardless of what you do with your body.
The Tsimane people used to cultivate or feed most of their food and bought only eight percent of it on the markets. Despite a staggering consumption of 2,738 calories a day, with 64 percent of the meals being carbohydrates, obesity, heart disease, and type 2 diabetes remained low
Despite the change in diet, the scientists are convinced that the tsimans continue to be active
WHAT IS CORONARY HEART DISEASE?
Coronary heart disease (CHD) is a leading cause of death both in the UK and worldwide. CHD is sometimes referred to as ischemic heart disease.
The main symptoms of CHD are: angina (chest pain), heart attack, heart failure.
However, not everyone has the same symptoms and some people may not have one before being diagnosed with CHD.
Coronary artery disease is the term that describes what happens when the circulation in your heart is blocked or interrupted by the formation of fatty substances in the coronary arteries.
Over time, the walls of your arteries may disguise with fatty deposits. This process is referred to as atherosclerosis and fat deposits are referred to as atheroma.
You can reduce the risk of CHD by making some simple lifestyle changes.
- healthy, balanced diet
- be physically active
- give up smoking
- Control of cholesterol level and blood sugar level
"If you're physically active, you can probably get away with more flexibility in your diet."
However, in the five years of the study, the intake of lard, oil, sugar and salt increased in the Tsimane population, especially in villages near market towns.
The researchers also compared the Tsimane diet with that of the neighboring tribe Moseten, which is culturally similar but considered western.
"They're predicting what Tsimane's health might look like in 20 years," said Professor Gurven.
"They outline what happens to the indigenous population over time.
"How can dietary changes increase the prevalence of heart disease and diabetes?"
According to an analysis of the diets of 229 Mosetans, the researchers found that they consumed 343 percent more sugar and used 535 percent more cooking oil than the Tsimane.
The study was published in the American Journal of Clinical Nutrition.
Mr. Kraft is worried that this kind of food could be the future of Tsimane. "This is a key time," he said.
"Roads are improving in the region, as is river traffic with the spread of motorized boats, so people are much less isolated than before.
"And it happens pretty fast, they're basically deep-fried and add lots of sugar to drinks if they can."
High sugar and oil consumption is believed to override Moseten's otherwise very healthy diet rich in fruits, vegetables, dairy and legumes.
However, they buy more of their food, including bread, dried meat and processed products, than the Tsimane.
"We are still analyzing their health indicators, but we expect Moseten to have more risk factors for diabetes and heart disease," said Professor Gurven.
The researchers found, however, that the Tsimane people are more active than the Mosetans, with their lifestyles strongly dependent on agriculture, hunting, fishing and foraging. They also rest due to higher infection rates.