Data from the Advanced Cognitive Training for Independent and Vital Elderly, involving 701 older adults (mean age 73.6) with normal weight, 1,081 overweight, and 902 who were obese, found that memory training provided only one-third the benefit to older adults with obesity compared with the benefit it provided to normal-weight older adults.

Participants were followed for 10 years. Over that time, the effects of training in reasoning and speed of processing didn’t differe between the weight groups. However, the effect of memory training on obese participants was just 38% of that observed in participants with normal-weight BMI.

Memory training focused on improving verbal episodic memory through instruction and practice in strategy use. Reasoning training focused on improving the ability to solve problems that contained a serial pattern. Speed training focused on visual search and the ability to process increasingly more information presented in successively shorter inspection times.

Of the participants, three-quarters were women; three-quarters were white and one-quarter were African-American.

https://www.eurekalert.org/pub_releases/2017-01/iu-oaw011017.php

Clark, D. O., Xu, H., Callahan, C. M., & Unverzagt, F. W. (2016). Does Body Mass Index Modify Memory, Reasoning, and Speed of Processing Training Effects in Older Adults. Obesity, 24(11), 2319–2326. https://doi.org/10.1002/oby.21631