Eating a high-fat diet in your 20s and 30s heightens the risk of ill-health later on – and not just because of weight gain.
According to researchers at Qingdao University, China, fatty foods cause a reduction in, and mutation of, so-called ‘good’ bacteria in the gut.
Specifically, an unhealthy diet modifies microbiomes – which break down food in the stomach – and sparks a rise in inflammatory markers throughout the body.
The data, published online in the journal Gut, raises fears this could sow the seeds of metabolic disorders, such as diabetes, heart disease and stroke, over the long term.
Taste test: Researchers at Qingdao University, China, studied 217 healthy 18 to 35-year olds
The researchers set out to see if different levels of dietary fat alter gut bacteria in healthy young adults from China.
Dietary habits in the Asian country are moving from being low-fat, high-carb to relatively high in fat and low in carbohydrates.
The researchers divided 217 healthy 18 to 35-year-olds of normal weight into three dietary groups.
The participants then received different ratios of carbs – white rice and wheat – and fat – mainly soybean oil.
Fibre and protein intake was kept the same between all the participants.
The three end diets were either low fat, where lipids made up 20 per cent of the participants’ energy intake.
Moderate fat – equal to 30 per cent of energy intake – or high fat – where lipids accounted for 40 per cent of energy intake.
Each participant stuck to their particular diet for six months.
Its impact on their gut bacteria and inflammatory markers was assessed in blood and faecal samples taken at the start and end of the experiment.
After six months, participants in all three groups lost weight, with those on the low-fat diet shedding the most.
But certain changes, with potential implications for long-term heath, were only evident in the samples from the high-fat group.
Warning: The data, published online in the journal Gut, fears this can sow the seeds of metabolic disorders, such as diabetes, heart disease and strokes over the long term
Although there were no major changes in the overall volume of gut bacteria among the three groups, the number of beneficial bacteria that produce short-chain fatty acids, including butyrate, only increased in the low-fat diet group.
By contrast, the numbers of these beneficial bacteria fell in the high-fat group.
And the number of ‘bad’ bacteria found in the guts of people with type 2 diabetes, for example, had increased.
Certain bacteria, such as Blautia species – which are associated with lower cholesterol levels – were abundant among those on the low-fat diet.
Bacteroides species, which are associated with elevated cholesterol levels, were more common among those on the high-fat diet.
What’s more, the higher-fat diet was associated with significant and potentially detrimental changes in long chain fatty acid metabolism.
This resulted in higher levels of chemicals that are thought to trigger inflammation.
The opposite was true for the low-fat diet.
The researchers emphasise sampling was only done at the start and end of the trial.
And a more complete picture of microbial changes would have emerged with more frequent sampling.
As all three groups lost weight, it is also not entirely clear whether the weight loss prompted the changes seen, or vice versa.
And as the participants were all young, healthy and a normal weight, the findings might not be more widely applicable, they add.
But the findings do seem to illustrate the need to curb dietary fat, the scientists suggest.
‘Compared with a lower fat diet, long-term consumption of a higher fat diet appears to be undesirable….for young healthy adults whose diet is in transition from the traditionally consumed lower fat, higher carbohydrate diet to one characterised by an appreciably higher fat content,’ they concluded.
Their findings might also have implications for other countries.
‘These findings might also have relevance in developed countries in which fat intake is already high,’ the researchers added.