Table 1 Data extraction table for the evaluated studies
Authors | Study design | Population | Obesity variable | Memory assessment | Assessment of diet | Assessment of exercise | Results |
|---|---|---|---|---|---|---|---|
Conforto and Gershman (1985) [9] | Cross-sectional | 30 Obese and 30 non-obese participants | BMI | Word list recall of food and non-food words | No | No | No significant association between BMI and memory recall |
Cournot et al. (2006) [7] | Prospective | 1660 Middle-aged men and 1576 middle-aged women | BMI | Word list learning | No | Yes | Independent of physical activity, higher BMI was associated with worse memory function for both the cross-sectional and prospective analyses |
Gunstad et al. (2006) [8] | Cross-sectional | 486 Participants, age range, 21–82 years | BMI | Word list learning | No | No | Obese individuals, compared to normal weight and overweight individuals, learned and recognized fewer words |
Dore et al. (2008) [85] | Cross-sectional | 917 stroke- and dementia-free adults; mean age = 62 years | Waist circumference, waist/hip ratio | Verbal memory | No | Yes | Both waist circumference and waist/hip ratio were significantly inversely associated with memory, but this was attenuated when physical activity was controlled for |
Nilsson and Nilsson (2009) [10] | Cross-sectional | Four samples from the Betula study were evaluated | BMI and waist/hip ratio | Sentence learning | Yes, but not factored in the analysis | No | No significant main effects associations between BMI and memory |
Smith et al. (2010) [89] | Experimental | 124 Overweight adults with high blood pressure; mean age = 52 years | BMI and DXA | Verbal paired associates | Yes | Yes | Those in the DASH Diet + WM (weight management) group had a reduction in weight and an improvement in memory after the 4-month intervention |
Gunstad et al. (2011) [86] | Prospective | 150 Adults (109 bariatric surgery patients and 41 obese controls) | BMI | Verbal list learning task; digit span forward | No | No | A significant group x time interaction effect was observed, noting that bariatric surgery patients, compared to the obese controls, improved on all indices of memory function 12 weeks post-operatively |
Gonzales et al. (2012) [64] | Cross-sectional | 55 Adults, aged 40–60 years | BMI | CVLT-II; RCF recall | No | No | BMI was not directly associated with memory, however, there was an indirect association between BMI and memory via mI/Cr (myo-inositol/creatine) |
Katz et al. (2012) [97] | Cross-sectional | 138 Women with systemic lupus erythematosus; mean age = 48 years | BMI, DXA, waist circumference | CVLT-II; rey complex figure test copy trial | No | Yes | Obesity was not associated with memory function |
Miller et al. (2013) [87] | Prospective | 137 Adults (95 bariatric survey patients and 42 obese controls) | BMI | Verbal list learning task; digit span forward | No | No | A significant group x time interaction effect was observed, noting that bariatric surgery patients improved on all indices of memory function 12Â months post-operatively |
Alosco et al. (2014) [88] | Prospective | 86 Adults (63 bariatric surgery patients and 23 obese controls) | BMI | Verbal list learning task; digit span forward | No | No | A significant group × time interaction effect was observed, noting that, relative to obese controls, bariatric surgery patients showed improvements in memory from baseline to 12 weeks and 24 months post-operatively |
Boraxbekk et al. (2015) [98] | Experimental | 20 Overweight post-menopausal women (Mage = 61 years) | BMI | fMRI assessment of a face–name paradigm to assess brain responses related to episodic memory. | Yes; randomized into a modified Paleolithic-type diet (PD) or a diet per Nordic Nutrition Recommendations (NNR) | Yes | Both diets reduced weight after the 6-month follow-up period. Memory performance improved after the 6-month period, with no differences between the diet groups. Brain activity increased in the hippocampus, prefrontal cortex and temporal gyri, without differences between diets. Neither of the groups significantly changed their physical activity levels across the two assessment periods |
Cheke et al. (2016) [99] | Cross-sectional | 50 Participants 18–35 years | Classified as obese, overweight, or normal based on BMI | What-where-when assessment (Treasure Hunter Task) | No | No | Higher BMI was associated with impaired performance on spatial, temporal, and item memory, as well as the ability to bind these elements together. Results were attenuated when considering demographic parameters |
Cheke et al. (2017) [14] | Cross-sectional | 34 Adults 18–36 years | Classified as obese or normal based on BMI | What-where-when assessment (Treasure Hunter Task), with brain activity assessed via fMRI | No | No | Compared to lean participants, obese participants had reduced functional neural activity in the angular gyrus, anterior prefrontal cortex, precuneus, hippocampus, parahippocampal gyrus |