It’s a debate that’s raged for years in health circles – which is worse, fat or sugar?
In the late 20th century and early 2000s, fat was reviled after being regularly linked to heart disease and high cholesterol.
But more recent research has shown that sugar is the enemy, with high-fat diets like keto earning praise from the scientific community.
A new study claims to have put the debate to the ultimate test – by studying which kills you faster, a high-fat or high-carb diet.

Researchers have found that a low-fat diet can significantly extend a person’s lifespan, while low-carb diets actually increase the risk of premature death (file photo)
Researchers have found that adopting a low-fat diet can reduce the risk of death by up to 34% each year. Meanwhile, low-carb diets increased mortality risk by up to 38%.
“Our results support the importance of maintaining a healthy LFD with less saturated fat for preventing all-cause and cause-specific mortality in middle-aged and older people,” the researchers wrote.
“In this study, all scores (low-fat diet) were associated with lower total mortality, indicating remarkable health benefits of reducing dietary fat to regain health.
“Our results were similar to those of several previous large-scale prospective cohort studies and randomized controlled trials, which also suggested reductions in dietary saturated fat.”
In their research, published Wednesday in the Journal of Internal Medicine, researchers from Harvard University, in Cambridge, Massachusetts, and Tulane University, in New Orleans, Louisiana, teamed up with Chinese scientists.
They collected data going back to the 1990s on 371,159 Americans, aged 50 to 71 at the start of the study.
Using the NIH-AARP Diet and Health Study, a survey launched in 1995 to assess links between diet and chronic disease in older adults, they looked for links between diet and lifespan.
In the survey, participants were asked how often they ate 124 different foods.
Using this information, the researchers calculated how often a person ate carbohydrates and fats.
Participants were divided into groups, with the 20% who ate the least carbs placed in a control group and compared to the 20% whose diet had the most carbs.
Going further, they categorized people as having a “healthy” or “unhealthy” low-fat or low-carb diet based on whether they got food from “high” or “low” quality sources.
For example, someone on a low-fat diet who ate lots of lean meat and vegetables would be on a “healthy” diet, while someone who ate refined sugars and processed foods was considered to have an “unhealthy” diet. .
They found that people who followed a low-fat diet, whether healthy or not, significantly reduced their risk of premature death, compared to people who followed a high-fat diet.
The risk of dying from any cause each year was down 21% for people on a low-fat diet. If it was a healthy diet, the risk of death dropped by 34%.
Those on an unhealthy low-fat diet still reduced their mortality risk by eight percent compared to their peers on an unhealthy, high-fat diet.
Meanwhile, following a low-carb diet was a pathway to an early death. People following a keto-like diet were 28% more likely to die from any cause compared to their high-carb peers.
Participants on an unhealthy low-carb diet increased their mortality risk by 38% each year.
Low-fat diets have long been favorites of people trying to lose weight and improve their overall health.
These diets will focus on eating fruits, vegetables, and lean meats while cutting out fatty oils.
Saturated and trans fats were particularly marked as being to be avoided. The former is often found in red meat, butter, cheese, and whole milk. The latter is common in processed and fried foods.
However, there are healthy fats. Monounsaturated and polyunsaturated fats found in olive oil, fish, and nuts are known to help maintain cholesterol levels and improve brain health.
Fat can also be used as an energy source for the body, with some claiming that it is healthier to train the body to use it as a primary energy source.
This has led to the rise of ketogenic diets, also known as “keto”.
The first to gain prominence was the Atkins diet, developed by cardiologist Robert Atkins in the 1960s.
These diets severely limit the number of carbohydrates a person consumes and instead consume large amounts of protein and fat.
People on keto will drop sugars, breads, and starches such as potatoes and broccoli, and other carbohydrate-rich foods.
Instead, their diet will consist of meat, eggs, dairy products, and leafy green vegetables.
While keto has won high profile endorsers, such as NBA star LeBron James and beauty mogul Kim Kardashian, it has also had many skeptics.