They are a remote Amazonian tribe who have been found to have the ‘healthiest hearts ever studied’.
But now scientists fear a surge in cases of heart disease and obesity among the Tsimane community in lowland Bolivia.
Researchers say the 6,000-strong tribe are becoming less isolated because of improvements to road and river transport links.
And this is affecting their diet, as figures show the tribe are buying 300 per cent more sugar and cooking oil than five years ago.
Researchers worry the global spread of western diets will cause obesity, type 2 diabetes and heart disease rates to spike in healthy communities.
The Tsimane have low rates of obesity and type 2 diabetes, as well as healthy blood pressure and cholesterol levels.
Researchers at the University of California, Santa Barbara, asked 1,299 Tsimane adults to complete food questionnaires.
They were asked to recall what they ate over the past day several times between 2010 and 2015.
‘Our prior work showed that the Tsimane have the healthiest hearts ever studied,’ senior author Professor Michael Gurven, said.
‘So naturally there’s a lot of interest in understanding why and how.’
At the start of the study, the Tsimane diet was high in calories with between 2,422 and 2,736 being consumed a day.
More than 60 per cent of these calories came from carbs, with them eating 376 to 423g a day – mostly from plantain and rice.
The rest of their diet, which consisted heavily of fish and game, was made up of around 119 to 139g of protein and between 40 and 46g of fat.
Despite their calorific diets, they still maintained their health, with nine out of ten having clear arteries.
The researchers, led by Thomas Kraft, also said the elderly Tsimane people even had the blood vessels of those in their 50s.
Their active lifestyles is thought to be what kept them so healthy, with the average adult taking 17,000 steps a day compared to an American’s 5,100.
Tsimane people were also found to grow or forage most of their food and bought just eight per cent of it from markets.
But despite their simple diet, they had much higher levels of the heart-healthy nutrients potassium, magnesium and selenium that Americans.
Their fibre intake was also almost twice that of a US resident. They were, however, lacking in calcium, and vitamins D, E and K.
‘They’re physically active – not from routine exercise, but from using their bodies to acquire food from their fields and the forest,’ Professor Michael Gurven, senior author of the study, said.
‘You can’t look at what you’re eating irrespective of what you’re doing with your body.
‘If you’re physically active, you can probably get away with more flexibility in the diet.’
But over the study’s five years, the Tsimane people’s intake of lard, oil, sugar and salt increased, particularly in villages near market towns.
The researchers also compared the Tsimane diet to that of the neighbouring tribe Moseten, which is culturally similar but considered more western.
‘They provide a forecast of what Tsimane health might look like 20 years from now,’ Professor Gurven said.
‘They represent what is happening to many indigenous populations over time.
‘To what extent may changes in their diet increase the prevalence of heart disease and diabetes?’
After analysing the diets of 229 Moseten people, the researchers found they ate 343 per cent more sugar and used 535 per cent more cooking oil than the Tsimane.
The study was published in The American Journal of Clinical Nutrition.
Mr Kraft worries this way of eating may be the future for the Tsimane. ‘This is a key time,’ he said.
‘Roads are improving in the area, as is river transport with the spread of motorised boats, so people are becoming a lot less isolated compared to the past.
‘And it’s happening at a pretty rapid pace. They’re basically deep frying and adding lots of sugar to drinks when they can.’
High sugar and oil consumption is thought to override the Moseten’s otherwise very healthy diet, which is high in fruits, vegetables, dairy and legumes.
They do, however, buy more of their food, including bread, dried meat and processed produce, than the Tsimane.
‘We’re still analysing their health indicators, but we expect the Moseten to show more risk factors related to diabetes and heart disease,’ Professor Gurven said.
The researchers noted, however, the Tsimane people are more active than the Moseten, with their lifestyles relying heavily on farming, hunting, fishing and foraging. But they also rest more due to higher rates of infection.