NMU 357 – High Fat-High Sugar Diet Has Negative Impact on Cognitive Ability

Nutrition/Natural Medicine Update No 357 (May 4, 2025)

with Dr. James Meschino

Topic: High Fat-High Sugar Diet Has Negative Impact on Cognitive Ability

Source: Int J Obesity (April 2025)

A study published in the Journal of Obesity in April 2025 is the first to show that humans fed a high fat, high sugar diet (particularly high refined sugar and high saturated fat diet) experienced impaired spatial navigation, which is the ability to remember a path from one location to another. Spatial navigation requires a highly functioning hippocampus; the part of the brain that consolidates short-term memory into long-term memory. Loss of short-term memory in dementia and Alzheimer’s disease involves a decline in function of the hippocampus, with concomitant atrophy of this area of the brain. More and more studies are showing that a high fat, high refined sugar diet increases risk of dementia and Alzheimer’s disease.

This study was the first to test spatial navigation ability in young adults 18-38 years of age. The results showed that those who consumed a high fat, high sugar diet showed detrimental effects on their spatial navigation ability – indicating sub-optimal functioning of their hippocampus in the brain. As Dr. Tran said in the follow-up interview, “We’ve long known eating too much refined sugar and saturated fat brings the risk of obesity, metabolic and cardiovascular disease and certain cancers. We also know these unhealthy eating habits hasten the onset of age-related cognitive decline in middle age and older adults. This research gives us evidence that diet is important for brain health in early adulthood, a period when cognitive function is usually intact.”

A number of studies over the years have shown that high fat, high sugar diets increase risk of dementias and a decline in spatial navigation ability. For example, epidemiological studies have shown that intake of foods high in fat and sugar by middle-aged and older adults predicts faster rates of normal age-related cognitive decline and increased risk of neurological disorders. And the deleterious effects of this diet on cognition are not confined to the middle-aged and elderly. Epidemiological studies have found evidence of diet-induced cognitive impairments across childhood and adolescence. Rodent studies have confirmed that consumption of foods that are high in fat and sugar (HFHS) leads to impairments in cognition, especially on tasks requiring the hippocampus and surrounding brain areas. These studies have also shown that cognitive deficits occur rapidly, well in advance of diet-induced increases in body weight and associated metabolic changes. For example, Tran and Westbrook found that rats fed a Western style, HFHS diet for as little as one week exhibited deficits in a hippocampal-dependent place recognition memory task.

The bottom line is that evidence strongly implicates a high fat, high sugar diet, as an important risk factor for cognitive decline in later life, beginning with detrimental effects on spatial navigation seen in 20-, and 30-year-olds. For many reasons I suggest that you do your best to avoid foods high in saturated fat and be very careful with your consumption of refined and starchy carbohydrate foods. Remain at your ideal body weight, exercise daily if possible, and get sufficient sleep. These are some lifestyle basics that can help prevent type 2 diabetes, metabolic syndrome, cardiovascular disease, obesity, certain cancers and age-related dementias and Alzheimer’s disease, according to published data.

I’ve included the reference for this information in the text below.

References:

Tran D. et al. Consumption of a diet high in fat and sugar is associated with worse spatial navigation ability in a virtual environment. Int J Obesity. 2025 (April 17) Consumption of a diet high in fat and sugar is associated with worse spatial navigation ability in a virtual environment | International Journal of Obesity

High-fat, high-sugar diets impact cognitive function. Medscape. April 21, 2025. High-fat, high-sugar diets impact cognitive function | ScienceDaily

Eat Smart, Live Well, Look Great,
Dr. Meschino