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Diets High in Fat and Sugar Are the Cause of Poor Performance.

Excessive consumption of foods high in fat and sugar has been linked to a decline in performance on hippocampus-dependent memory tasks.

A recent study has revealed that in these tasks, success rates were lower, and reaction times were longer among the participants. The publication of this study can be found in Physiology & Behavior.

Throughout the last century, there has been a significant global shift towards the utilization of industrially produced, highly processed foods. Instead of preparing meals within our households from raw ingredients, modern meals are primarily composed of ingredients that have undergone some degree of processing. In many cases, sugars and fats are added to these processed foods. These additions enhance the flavor and overall palatability of the meals but also result in an increase in their calorie content.

High-fat and high-sugar diets are referred to by researchers as diets primarily composed of food items with abundant added sugar and fat. In such diets, one typically finds an abundance of pastries and baked goods, confections and chocolates, fast food meals like burgers, French fries, and fried chicken, as well as sweetened beverages such as soft drinks, energy drinks, flavored juices, or sweetened teas, along with processed snacks like chips, crackers, or snack cakes, breakfast cereals, sauces, dressings, and similar food items.

It has been suggested by studies that an excessive consumption of high-fat and high-sugar foods may lead to adverse effects on the hippocampus, which, in turn, can impact memory functions reliant on this region. The investigation was undertaken by Selena Atak and her colleagues from the University of Michigan-Dearborn, with the hypothesis that individuals who consume substantial quantities of high-fat and high-sugar foods would exhibit poorer performance on memory-related tasks and report more frequent everyday memory lapses.

The anticipation of these outcomes also included the expectation that a high-fat and high-sugar diet would be associated with a decline in performance on executive functioning tasks. Executive cognitive functions, which encompass skills such as planning, organization, impulse control, attention shifting, and working memory, were identified as higher-level mental processes that play a role in guiding goal-directed behaviors, decision-making, and self-regulation.

To assess these hypotheses, an online study involving 340 participants recruited from Amazon MTurk was conducted by the researchers. The participants, predominantly female and aged between 18 and 35, were tasked with completing various assessments and questionnaires pertaining to their dietary behaviors, memory, and executive functioning.

The study was conducted online through Qualtrics, where participants responded to inquiries regarding their dietary patterns using the Dietary Fat and Sugar Short Questionnaire. Additionally, they engaged in four distinct memory evaluations, namely the Pattern Separation Task, the Associative Memory Task, the Word Memory Task, and a subjective memory complaints assessment using the Everyday Memory Questionnaire-Revised. Furthermore, they completed two executive functioning assessments: the Trail Making Task, which evaluates attention-shifting ability and cognitive flexibility, and the Stroop task, designed to gauge cognitive processing speed and inhibitory control.

Data on participants’ height and weight, enabling the calculation of body mass index, as well as information regarding depression and anxiety symptoms (via the Depression Anxiety Stress Scale-21), eating habits (utilizing the Three-Factor Eating Questionnaire), severity of sleep disturbances (using the PROMIS-level 2 sleep disturbance-short form), and physical activity routines (including questions about exercise frequency, duration, and intensity) were also collected by the researchers.

The results indicated that there was a positive association among all memory measures — individuals who exhibited better performance on one memory task tended to perform better on all the others. Improved memory performance was related to a reduction in complaints concerning everyday memory lapses. It was also tied to enhanced performance on executive tasks.

Higher consumption of high-fat and high-sugar foods was associated with lower scores on all memory tasks among participants. The sole exception pertained to the word recognition task. Moreover, these participants experienced delayed reaction times on the Stroop task. However, when factors like depression, anxiety, eating behaviors, sleep quality, height, and weight were taken into account by the researchers, the connection between high-fat and high-sugar diets and one of the memory tasks ceased to be evident. The same held true for the link with self-reported memory difficulties in daily life.


It has been demonstrated that there is an association between the intake of high-fat and high-sugar foods and diminished hippocampus-dependent memory. Additionally, a high-fat and high-sugar diet was found to predict decreased executive functioning in terms of attention-shifting ability and processing speed. Consequently, it has been established that a high-fat and high-sugar diet is linked to reduced executive control, potentially contributing indirectly to poorer memory among high-fat and high-sugar consumers. Given the scarcity of human research, our findings are valuable and provide evidence for the role of diet in impairing critical cognitive functioning, which may, in turn, hinder the adoption of a healthy lifestyle, as concluded by the study authors.

This study illuminates the connection between dietary patterns and cognitive performance. Nevertheless, it is important to acknowledge certain limitations in the study design. Notably, causation cannot be inferred due to the study’s design. Furthermore, the researchers did not account for participants’ hunger levels at the time of the study, and the assessment of dietary habits relied solely on self-reports.


Overconsumption of high-fat and high-sugar (HFS) diet may affect the hippocampus, and consequently, memory functions. Yet, converging evidence is needed to demonstrate that the type of memory affected by HFS diet consumption is indeed hippocampus dependent. Moreover, the extent to which HFS diet can also affect executive functioning, and indirectly affect memory requires further examination. In this online study, we asked 349 young adults to report their HFS diet consumption and complete a word memory task, the Everyday Memory Questionnaire, and importantly two memory tasks that have been shown to robustly engage the hippocampus, i.e., the Pattern Separation and Associative Memory Tasks. Participants also completed two executive functioning tasks, the Trail Making Task (TMT) and the Stroop Task. These measures assess attention/cognitive flexibility and the ability to inhibit cognitive interference, respectively. After controlling for confounding variables, we found that participants who reported higher level consumption of a HFS diet performed worse on the Pattern Separation Task and that higher HFS intake was significantly associated with poorer TMT task performance and longer Stroop average reaction time (RT). TMT and Stroop RT scores indicative of reduced executive function also partially mediated the relationship between HFS diet and memory performance on the pattern separation task. Taken together, our results provide converging evidence that HFS diet may impair hippocampus-dependent memory. HFS diet may also affect executive functioning and indirectly impair memory function. The findings are consistent with human subject and animal studies and call for further investigations on the psychological and neural mechanisms underlying the dietary effects on cognitive processes.

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