Junk food doesn’t just make you fat; a new study shows young children and adolescents who consume fatty and unhealthy foods over an extended period can damage the young brain as it matures, impairing cognitive functions in adulthood. Scientists at ETH Zurich and the University of Zurich reached this conclusion after performing a study comparing the impact on the brains of juvenile and adult mice on being fed either an extremely high-fat diet (over 60 per cent of total calories) or normal food.
The fat-rich diet contained excessively high levels of saturated fats – most commonly found in fast foods, charcuterie products, butter and coconut oil. After just four weeks on a high-fat diet, the first signs of impairment in the cognitive functions of young mice were detected – even before they actually started to gain weight.
The prefrontal cortex, responsible for the executive functions of the human brain, is particularly vulnerable to negative environmental experiences such as a poorly balanced diet. The region looks after memory, planning, attention, impulse control and social behaviour.
The researchers failed to identify comparable changes in the behaviour of mature mice that had been fed a high-fat diet over an extended period. The results of this mice study, the researchers say, are readily translatable to humans.
Whole-fat milk ‘makes for leaner children’
Children who drink whole milk are leaner and have higher vitamin D levels than those who drink low-fat or skimmed milk, new research suggests. In the study, published in The American Journal of Clinical Nutrition, children who drank whole milk (3.25 per cent fat content) had a Body Mass Index 0.72 units lower than those who drank 1 or 2 per cent milk. That’s comparable to the difference between a healthy weight and being overweight, says lead author Dr Jonathon Maguire, a paediatrician at St Michael’s Hospital in Toronto.
The study, which looked at 2,745 children aged two to six years, also found that children who drank one cup of whole milk each day had comparable vitamin D levels to those who drank nearly three cups of one per cent milk. This could be because vitamin D is fat soluble, meaning it dissolves in fat rather than water. Milk with higher fat content can therefore contain more vitamin D.
Maguire hypothesises that children who drank whole milk felt fuller than those who drank the same amount of low-fat or skimmed milk, and therefore were less likely to eat other foods that are less healthy or higher in calories. Children who drink lower fat milk may actually consume more calories overall than those who drink whole milk.
The study’s findings differ from Health Canada, US National Institutes of Health and American Academy of Paediatrics guidelines recommending two servings of low fat (1 or 2 per cent) milk for children over the age of two to reduce the risk of childhood obesity.
Nepalese porters do it the hard way
Nepalese porters are known for an almost superhuman ability for carrying heavy loads, and Belgian researchers have found there is no secret energy-conserving trick behind that ability other than brute power.
A research team led by Norman Heglund from the Université catholique de Louvain shipped one tonne of equipment from Belgium to Nepal and selected Phakding, in the Everest valley on the path to the weekly bazaar in Namche, as their base. Heglund hired about 30 porters and a dozen yaks to haul the equipment half a day’s hike up to the settlement.
The team recruited volunteer porters to walk back and forth across a force plate at various speeds, carrying loads ranging from 0 to 154 per cent of their weight in baskets suspended from straps across their foreheads. The team also filmed the porters’ movements, and later used the footage to calculate the amount of mechanical work performed by each of the participants’ limbs as they carried their burdens.
Previously, Heglund had investigated how the Kikuyu and Luo women in Kenya carry water on their heads, and he discovered that they have a unique trick where they transfer their weight from one foot to the other extremely effectively. This allows them to conserve up to 80 per cent of the energy from the previous step.
But the Nepalese porters do “nothing special”, says Heglund. Instead, the porters move at a relatively slow speed of around 3-4 kilometres per hour and took frequent breaks, walking sometimes for as little as 15 seconds before resting for another 45 seconds, to ensure that they never had to revert to costly anaerobic metabolism.