A claim you hear on longevity podcasts
The claim checked: Young adults who eat more sugar and saturated fat do worse on memory tests Hear it at 1:00:47
Six of seven studies found the link, all in young adults. In one trial, 102 lean students who ate a Western-style diet for a few days did worse on memory tests that rely on the hippocampus, the brain's memory hub. Other studies tied higher habitual intake of fat and sugar to worse memory. The effects were small: in 699 people the link was real but slight. One study of 38 women pointed to saturated and trans fats in particular.
Computed from 7 studies that test this point, each judged by two readers, in full. 3 more studies are waiting for a full read and do not count yet.
“there was connections between habitual sugar consumption and saturated fatty acid consumption and how well they did on these memory tests.”
On tape: studies by Stevenson and colleagues in healthy undergraduates, linking habitual sugar and saturated fat intake to memory tests that rely on the hippocampus. This study matches those details; we read only its abstract. Higher reported saturated fat and refined sugar intake is associated with reduced hippocampal-dependent memory and sensitivity to interoceptive signals. Behav Neurosci, 2011. Two cross-sectional studies in people, Human participants grouped by self-reported intake of saturated fat and refined sugar (the abstract gives no ages).
What it found
“Study 1, using a cross-sectional design, revealed that self-reported HFS diet was associated with poorer performance on hippocampal sensitive memory tasks but not other neuropsychological control measures.”
How the authors extend it
“Together, these findings reveal an association between HFS consumption and poorer hippocampal function in human participants, consistent with findings from animal-based studies.”
Not stated in the text we read (abstract only; no free full text).
controlled trial · 2017
“In conclusion, we show that brief consumption of a Western-style diet leads to impairments in HDLM and interoception in healthy lean young adults.”
A four-day Western-style dietary intervention causes reductions in hippocampal-dependent learning and memory and interoceptive sensitivity. PLoS One
Who: 102 lean (BMI < 25) university students with low habitual fat and sugar intake (mean age ~20-21), Macquarie University
PMID 28231304
other primary study · 2020
“The WS-diet group had a significantly lower retention score on Day 8 ( M = 92.0% [95%CI, 88.5–95.4]) than controls ( M = 97.0% [95% CI, 94.2–99.9]).”
Hippocampal-dependent appetitive control is impaired by experimental exposure to a Western-style diet. R Soc Open Sci
Who: lean, healthy young adults aged 17-35 (mean about 22 y) at Macquarie University who habitually ate a healthier-than-average diet
PMID 32257311
other primary study · 2016
“Overall, these findings suggest a slower VPA learning rate is associated with higher reported intake of saturated fat and refined sugar (see Figure 1).”
A high-fat high-sugar diet predicts poorer hippocampal-related memory and a reduced ability to suppress wanting under satiety. J Exp Psychol Anim Learn Cogn
Who: Healthy adults aged 17-35 with BMI about 17-26, recruited from a Macquarie University psychology participant pool and the wider university community, selected from the upper and lower quartiles of habitual saturated fat and refined sugar intake
PMID 27598061
other primary study · 2023
“Thus all three Experiments provided further evidence that habitual intake of fat and sugar was associated with impaired memory, adding significantly to the existing published evidence both from similar correlational studies [ 10 , 11 , 17 , 72 ] and studies using short-term overexposure to fat and sugar [ 18 , 19 ].”
Habitual intake of fat and sugar is associated with poorer memory and greater impulsivity in humans. PLoS One
Who: Mostly young adult volunteers recruited at the University of Sussex (mean ages 21.4-22.6 years): 90 women (Exp 1), 120 adults (Exp 2), 286 adults (Exp 3)
PMID 37616232
other primary study · 2025
“Young adults who reported consuming more HFHS foods across that period were worse at remembering the target location in the maze.”
Consumption of a diet high in fat and sugar is associated with worse spatial navigation ability in a virtual environment. Int J Obes (Lond)
Who: 55 University of Sydney students (mean age 20) who completed a virtual-reality spatial navigation task
PMID 40247089
other primary study · 2025
“The model predicting total VPA score from total DFS score was sig nificant, (r2 = 0.006, F(1, 697) = 4.5, p = 0.034), with a small negative association between DFS and VPA total scores, (β = − 0.080 [− 0.154, − 0.006], p = 0.034) (Fig. 5).”
Does habitual caffeine consumption moderate the association between a high fat and sugar diet and self-reported and episodic memory impairment in humans? Physiol Behav
Who: Healthy volunteers aged 18-45, mostly 18-25 (mean ages 20.8 and 19.5): Experiment 1 n = 1000, Experiment 2 n = 699
PMID 40885226
other primary study · 2013
“In summary, we found evidence that high intake of saturated and trans fats in particular, and possibly MUFA, may adversely affect memory and learning even in relatively young women.”
Habitual fat intake predicts memory function in younger women. Front Hum Neurosci
Who: 38 women aged 25-45 (mean 32.7 y) in the UK, 23 with polycystic ovary syndrome and 15 matched controls
PMID 24376410
None.
The Precis Weekly
One email a week with the claims and episodes we checked, what the studies found and the minute each claim was said.
Free. Unsubscribe anytime.