A South American tribe with a highly active lifestyle has the healthiest arteries of any population yet studied, say researchers.
The Tsimane people, who live in the Bolivian Amazon, spend most of every day hunting, fishing, farming and gathering wild fruits and nuts, and follow a carbohydrate-based diet containing little protein and fat.
Scientists who examined hundreds of men and women from the group found that almost nine out of 10 had clear arteries showing no risk of heart disease.
Even in old age most remained in astonishingly good health.
Almost two thirds of people aged over 75 were nearly risk free and just eight per cent had a moderate-to-high risk level.
One 80-year-old had arteries resembling those of Americans in their mid-fifties.
US lead scientist Professor Hillard Kaplan, from the University of New Mexico, said: "Our study shows that the Tsimane indigenous South Americans have the lowest prevalence of coronary atherosclerosis (hardening and narrowing of the arteries) of any population yet studied.
"Their lifestyle suggests that a diet low in saturated fats and high in non-processed fibre-rich carbohydrates, along with wild game and fish, not smoking and being active throughout the day could help prevent hardening in the arteries of the heart.
"The loss of subsistence diets and lifestyles could be classed as a new risk factor for vascular ageing and we believe that components of this way of life could benefit contemporary sedentary populations."
While people living in cities are sedentary for more than half their waking hours, the Tsimane are inactive for only 10 per cent of the day.
Men spend an average of six to seven hours a day engaged in physical activity, while women are active for four to six hours, said the researchers, whose findings are reported in The Lancet medical journal.
The Tsimane diet largely consists of non-processed carbohydrates high in fibre, such as rice, plantain, manioc, corn, nuts and fruits.
Protein, from animal meat, accounts for only 14 per cent of the diet and fat makes up the same proportion.
Each member of the tribe consumes roughly 38 grams of fat per day, of which just 11 grams is saturated fat.
The researchers visited 85 Tsimane villages between 2004 and 2015 and measured heart disease risk by carrying out CT (computed tomography) X-ray scans on 705 adults aged 40 to 94.
Their lifestyle suggests that a diet low in saturated fats and high in non-processed fibre-rich carbohydrates, along with wild game and fish, not smoking and being active throughout the day could help prevent hardening in the arteries of the heart
Professor Hillard Kaplan
Similar scans of nearly 7,000 Americans in a previous study showed that only 14 per cent had no risk of heart disease.
Half were at moderate-to-high risk - a five-fold greater prevalence rate than that seen in the Tsimane population.
Members of the tribe also had low readings for heart rate, blood pressure, cholesterol and blood sugar.
But strangely, half the population had raised inflammation markers, despite this normally being seen as a risk factor for unhealthy arteries.
Co-author Professor Randall Thompson, from Saint Luke's Mid America Heart Institute, said: "Conventional thinking is that inflammation increases the risk of heart disease.
"However, the inflammation common to the Tsimane was not associated with increased risk of heart disease, and may instead be the result of high rates of infections."
The research is being presented at an American College of Cardiology conference taking place in Washington DC.
Professor Sir Nilesh Samani, medical director of the British Heart Foundation, said: "We already know that certain aspects of lifestyle increase your risk of heart disease, and we've been providing advice on these for many years now.
"This study simply adds to the wealth of research already done on this topic.
"There are some lessons we can learn from this study though.
"It may not be possible for people in the industrialised world to copy the Tsimane community's way of life, but there are certainly aspects of their diet and lifestyle, such as not smoking and eating a diet low in fat, that we can better incorporate into our lives to help reduce our risk of heart disease."