How the Western Diet Leads to Cognitive Decline and Obesity

What is the Western Diet

The Western diet is a diet that is high in saturated fats and sugars, red and processed meats, refined flour baked goods, and fast food. In addition, such a diet includes few vegetables and fruits, whole grains and dairy products.

The exact number of conditionally beneficial and harmful components of the diet is not indicated, but they can be roughly determined based on WHO recommendations .

A Western diet can be considered a diet in which:

  • The total amount of fat in the diet exceeds 30% of the daily calorie intake.
  • Saturated fats from meat and dairy products exceed 10% of your daily calorie intake.
  • Sugar makes up over 10% of total calories per day.
  • Consume less than 400 g of fruits and vegetables per day.

This type of diet is considered unhealthy because it increases the risk of stroke, colon cancer, kidney disease, and immune system dysfunction.

What’s more, it can hit cognition—the brain processes that help us perceive, process, and remember information, make plans, and control impulses.

How the Western Diet Affects Cognitive Function

The Western diet does not have the best effect on brain function, moreover, at any age.

In one experiment , children aged 7–9 years who consumed a lot of snacks and little fruit and vegetables noted a decrease in several cognitive functions, including inhibitory control, which suppresses unwanted stimuli, the ability to plan and organize.

Two other studies noted memory impairment in obese children with high fat diets.

In another experiment , the abilities of young people – college students were tested. It turned out that those who eat more chips, other snacks and chocolate bars and less fruits and vegetables have less control over attention and motor reactions than adherents of a healthy diet.

In another experiment , students who ate a Western diet performed worse on logic and memory tasks, functions associated with the hippocampus.

The situation is no better for the elderly. Foods high in saturated fat increase the risk of cognitive impairment in old age, and obesity reduces attention and concentration ability, and slows down information processing.

Moreover, for the deterioration of cognitive functions, it is not necessary to eat like this for many years – even a few days on a Western diet can adversely affect brain function. So, in one experiment , just four breakfasts with a high amount of saturated fat and sugar lowered the results in tests for different types of memory.

One study suggested that cognitive decline from a Western diet is more dependent on the hippocampus, a brain structure that is involved in memory storage, emotion formation, and spatial orientation. Here are some possible mechanisms:

  1. Decreased neurogenesis. A high intake of saturated fat and sugar reduces the formation of new neurons in the hippocampus.
  2. Increased permeability of the blood-brain barrier (BBB). This system regulates the transport of nutrients and protects the brain from neurotoxic substances. In obesity, an increased permeability of the BBB is observed, which in the future can lead to a lack of brain nutrition.
  3. Inflammation. The Western diet contributes to its occurrence and development, and this can disrupt the hippocampus.
  4. Violation of glucose transport. The brain needs glucose to function, and its transport to the brain depends on glucose transporter 1 (GLUT-1). A diet high in fat reduces its amount, which can negatively affect cognitive functions.
  5. Insulin resistance. An unhealthy diet can reduce the transport of insulin to the brain, reducing episodic memory.

Thus, the Western diet can reduce cognitive function, which in turn makes it difficult to control eating behavior.

How cognitive decline is related to appetite and weight

If the decision to eat or the choice of food depended only on the physiological need for energy, few people would suffer from excess weight. In real life, eating behavior depends on many factors:

  • Expectations. In one experiment , people rated food labeled “healthy” as less tasty, in another they rated “expensive” wine more, when in fact it was no different from “cheap” wine.
  • Memory. Memories of whether a meal is satisfying or not can affect how much you eat. In one experiment , they found that when people are reminded of what they ate during lunch, they choose a lighter snack .
  • Perception. In one experiment , people were served 300 or 500 ml of soup, while some were told the truth about the amount, while others were deceived. All participants who received information about 500 ml of soup in a bowl felt more full after 2–3 hours, regardless of how much they actually ate.
  • The ability to control. Overweight people often have a deficit in inhibitory control, which reduces their ability to suppress thoughts about food and food-related stimuli.

Scientists have suggested that people gain weight because of a malfunction in the system that determines how pleasant the same event can be – when it will provide a reward, and when it will not. And the already familiar hippocampus plays an important role here.

Using context, this brain structure decides whether something good is worth waiting for or whether everything pleasant has already ended. If the latter is true, the inhibitory association is turned on and the memory of the reward is muted.

This scheme of work is quite applicable to food. Food can be a reward when a person is hungry , and no pleasure when a person is full. Satiation signals are the context on which the hippocampus represses the pleasant memory of food.

A person is hungry – “it’s nice to eat, I’ll go eat.” A person is full – “eating is no longer pleasant, I’ll go do something else.” A person has eaten recently – “I’m not hungry yet, it will be unpleasant to eat, I won’t eat.”

If the work of the hippocampus is disrupted, the inhibitory mechanism does not turn on, and the memory of the reward from food is always preserved, even when a person is full.

As a result, he cannot stop in time and consumes more than he needs to be full, as well as snacking endlessly, regardless of how long ago he dined.

Can the vicious circle be broken?

The logical way to break the cycle of overeating and damage to the hippocampus is to switch to a healthy diet. First of all, it is worth reducing the amount of sweets and sugar, giving up fast food, fatty and processed meat, adding more vegetables and fruits, fish, nuts and whole grains to the diet.

Changes should be introduced gradually, without setting strict prohibitions and serious restrictions. Keep in mind that a lack of inhibitory control can make it harder to cut back on tasty foods and therefore drastic diets can trigger a relapse.

To quickly restore the work of the hippocampus, it is also worth increasing the amount of physical activity. Exercise promotes the formation of new neurons in this brain structure, keeps it healthy, improves cognitive functions and mood.

Smooth changes, healthy nutrition and sports will help restore the natural mechanisms that control the feeling of satiety and the desire to eat, so it will be much easier to maintain a healthy lifestyle.

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