A week of unhealthy eating can ‘damage a part of the brain, which means we normally DO NOT eat MORE’
Eating junk food for a week was enough to damage part of the brain so that we don’t eat when we are full, research suggests.
Study participants who ate an abundance of fast foods and high-fat milkshakes had become more hungry after seven days.
They performed worse on cognitive tests, with results suggesting that part of the brain called the hippocampus was affected.
The hippocampus normally prevents us from eating more food when we are full of suppressing memories of how delicious it is.
If it doesn’t work well, the memories are more powerful and we cannot resist more cake, chocolates and chips for us, the researchers believe.
The discovery sheds light on why people grabbed the biscuit can – instead of being hungry – and why it is so difficult to get out of a cycle of bad food.
Eating junk food for a week was enough to damage part of the brain so that we no longer eat when we are already full, research suggests
Experiments with animals have shown that poor nutrition quickly affects the hippocampus – an area with gray matter that regulates memory and appetite.
Now the phenomenon has been demonstrated for the first time in humans.
Chief author Professor Richard Stevenson of Macquarie University in Australia said: ‘When we see cake, chocolate or chips, for example, we remember how tasty they are to eat.
‘When we are full, the hippocampus normally suppresses these memories, which means we want to eat less.
THE WESTERN DIET STATED
The western diet is loosely defined as a full of fat and sugary foods such as hamburgers, fries and soft drinks.
People often eat food that is rich in
- Saturated fats
- Red meat
- “Empty” carbohydrates
- Junk food
And low in
- Fresh vegetables and fruit
- Whole grain
Health effects have been associated with issues such as hypertension, heart disease, diabetes, obesity, colorectal cancer and dementia.
“We found that lean healthy young people who were exposed to a week of junk food diet developed reduced hippocampal function and a relatively greater desire to eat junk food when they were full.”
He explained: “Junk food can then undermine self-control by increasing the desire.”
In the study, 110 male and female students from the campus were divided into two groups – half of whom were randomly selected to split on a Western diet for seven days.
They started by receiving a laboratory breakfast with a sandwich and a milkshake, rich in saturated fat and added sugar.
Their daily diet then included waffles and a main meal, dessert, and drink from a popular fast-food restaurant for an intake of more than 4,000 calories. They received cash to pay for it.
The others acted as a control, starting with a breakfast of a toasted sandwich and a milkshake, low in saturated fat and added sugar. They continued with their normal diet.
Before and after the participants assessed their taste and desire for tasty sugary grains such as Coco pops and Frosties in milk and snacks such as Vegemite and Nutella on toast.
The ranking went up among those who had eaten the junk food – even when the images were presented that were saturated.
They also performed worse in memory and learning tests focused on the hippocampus.
Interestingly, when these were repeated three weeks later after returning to their normal eating habits, these abilities returned to normal – suggesting that the damage could be reversed.
Because the damaged part of the brain is also involved in memory, researchers say it contributes to the evidence that an unhealthy diet increases the risk of Alzheimer’s disease.
Professor Stevenson, a food psychologist, said a number of studies have shown that the hippocampus is particularly vulnerable to environmental risks – such as unhealthy food.
He said: “It is for this reason that a Western diet – along with other factors – are known correlates of Alzheimer’s disease.
‘In conclusion, a large animal literature shows that a Western-style diet adversely affects the hippocampus.
“The current study suggests that something similar is happening in humans, because the one-week exposure causes a reduction in memory and learning performance, in addition to changes in appetite control, as measured by the will and sympathy tests.”
The study, published in the Royal Society’s Open Science journal, follows research that rats fed a 25 percent sugar diet were put in a state of fear when it was removed.
Their symptoms include chattering teeth and shakes – similar to those in people who withdraw from nicotine or morphine, the US team said.
Other studies in rodents have shown that sweet foods stimulate opioids or “pleasure chemicals” in the brain – suggesting that people may become too dependent on them.
WHAT WOULD A BALANCED DIET LOOK LIKE?
Meals should be based on potatoes, bread, rice, pasta or other starchy carbohydrates, ideally whole grain, according to the NHS
• Eat at least 5 servings of a variety of fruits and vegetables every day. All fresh, frozen, dried and canned fruit and vegetables count
• Basic meals on potatoes, bread, rice, pasta or other starchy carbohydrates, ideally whole grain
• 30 grams of fiber per day: this is the same as eating all of the following: 5 servings of fruit and vegetables, 2 whole-grain cereal cookies, 2 thick slices of whole-grain bread and a large baked potato with the skin on it
• Provide some alternatives to dairy or dairy products (such as soy drinks) with options for less fat and less sugar
• Eat some beans, legumes, fish, eggs, meat and other proteins (including 2 portions of fish every week, one of which must be fatty)
• Choose unsaturated oils and spreads and consume in small quantities
• Drink 6-8 cups / glasses of water daily
• Adults must have less than 6 g of salt and 20 g of saturated fat for women or 30 g for men per day
Source: NHS Eatwell guide