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 amount of conditionally beneficial and harmful components of the diet is not indicated, but you can roughly determine them based on recommendationsHealthy diet / World Health Organization WHO.

A Western diet can be considered a diet in which:

• Total fat in the diet exceeds 30% of the daily caloric 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, bowel 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 experimentN. Riggs, C. P. Chou, D. Spruijt Metz. Executive cognitive function as a correlate and predictor of child food intake and physical activity / Child Neuropsychology in children 7–9 years old, who consume a lot of snacks and few fruits and vegetables, a decrease in some cognitive functions, including inhibitory control, which suppresses unwanted stimuli, the ability to plan and organizations.

In two other studies noted1. N. A. Khan, C. L. Baym, J. M. Monty. Central adiposity is negatively associated with hippocampal‑dependent relational memory among overweight and obese children / The Journal of Pediatrics
2. C. L. Baym, N. A. Khan, J. M. Monty. Dietary lipids are differentially associated with hippocampal-dependent relational memory in prepubescent children / The American Journal of Clinical Nutrition memory impairment in children with obesity and a high percentage of fat in the diet.

In one more experimentA. J. Jasinska, M. Yasuda, C. F. Burant. Impulsivity and inhibitory control deficits are associated with unhealthy eating in young adults / Appetite tested the abilities of young people - college students. It turned out that those who eat more chips, other snacks and chocolate bars and less fruits and vegetables have poorer control of attention and motor reactions than adherents of a healthy diet.

In a different experimentH. M. Francis, R. J. Stevenson. Higher reported saturated fat and refined sugar intake is associated with reduced hippocampal‑dependent memory and sensitivity to interoceptive signals / Behavioral Neuroscience students who preferred a Western diet showed the worst results in logic tasks and memory are functions associated with the work of the hippocampus.

The situation is no better for the elderly. Foods high in saturated fat increasesM. H. Eskelinen, T. Ngandu, E. L. Helkala. Fat intake at midlife and cognitive impairment later in life: a population‑based CAIDE study. International Journal of Geriatric Psychiatry risk of cognitive impairment in old age, and obesity reducesJ. I. Cohen, K. F. Yates, M. Duong. Obesity, orbitofrontal structure and function are associated with food choice: a cross‑sectional study / BMJ Open attention and ability to concentrate, slows down the processing of information.

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. Yes, in one experimentT. Attuquayefio, R. J. Stevenson, M. J. Oaten. A four‑day Western‑style dietary intervention causes reductions in hippocampal‑dependent learning and memory and interoceptive sensitivity / PLoS One just four breakfasts high in saturated fat and Sahara reduced results in tests for different types of memory.

In one scientific work assumedT. L. Davidson, S. Jones, M. Roy, R. J. Stevenson. The Cognitive Control of Eating and Body Weight: It’s More Than What You “Think” / Frontiers in Psychologythat 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. Unhealthy diet can reduce transport insulin in 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 dependsT. L. Davidson, S. Jones, M. Roy, R. J. Stevenson. The Cognitive Control of Eating and Body Weight: It’s More Than What You “Think” / Frontiers in Psychology from many factors:

• Expectations. In one experimentR. Raghunathan, R. W. Naylor, W. D. Hoyer. The unhealthy = tasty intuition and its effects on taste inferences, enjoyment, and choice of food products / Journal of Marketing people found food labeled "healthy" to be less tasty friendL. Schmidt, V. Skvortsova, C. Kulen. How context alters value: the brain’s valuation and affective regulation system link price cues to experienced taste pleasantness / Scientific Reports “expensive” wine was rated higher, although in fact it did not differ from “cheap” wine.
• Memory. Memories of hearty food or not mayM. A. Irvine, J. M. Brunstrom, P. Gee. Increased familiarity with eating a food to fullness underlies increased expected satiety / Appetite affect how much you eat. In one experimentS. Higgs. Memory for recent eating and its influence on subsequent food / intake Appetite found that when people are reminded of what they ate during lunch, they choose a lighter snack.
• Perception. In one experimentJ. M. Brunstrom, J. F. Burn, N. R. Sell. Episodic memory and appetite regulation in humans / PLoS One people were served 300 or 500 ml of soup, but at the same time some were told the truth about the quantity, 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 assumedT. L. Davidson, S. Jones, M. Roy, R. J. Stevenson. The Cognitive Control of Eating and Body Weight: It’s More Than What You “Think” / Frontiers in Psychologythat 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 hungry, and not provide pleasure when he 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 disturbed, 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?

A logical way to break the vicious circle overeating and damage to the hippocampus will be the transition 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 the lack of braking control maybeT. L. Davidson, S. Jones, M. Roy, R. J. Stevenson. The Cognitive Control of Eating and Body Weight: It’s More Than What You “Think” / Frontiers in Psychology complicate the task of giving up the usual tasty food and reducing its quantity, and therefore rigid diets can provoke a breakdown.

To quickly restore the work of the hippocampus, it is also worth increasing the amount of physical activity. Exercises contributeS. Chieffi, G. Messina, I. Villano. Exercise Influence on Hippocampal Function: Possible Involvement of Orexin‑A / Frontiers in Phusiology the formation of new neurons in this brain structure, maintain its health, improve cognitive functions and mood.

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