People whose weight changed the least had the slowest decline in thinking ability, while those whose weight changed the most had two to four times the amount of cognitive decline. These individuals also experienced faster memory and thinking decline. It’s already known that being obese in middle age can raise the risk of brain decline later in life. Instead, the takeaway message is that sudden or repeated weight loss may be harmful to brain health, especially in later life. The team also suggests that older adults should monitor their weight at home in a consistent way.