Evidence from human and animal studies suggests that high-energy diets impair cognitive function. However, the conditions for such impairments are unclear as studies have differed in the type and duration of diet exposure as well as in the tasks used to assess deficits in cognition. Here, we focused on hippocampal-dependent tasks. We conducted separate meta-analyses of the results from rodent studies using: 1) different diets (high in fat, high in sugar, or high in both fat and sugar); and 2) different tasks to assess hippocampal-dependent spatial learning and memory (water maze, place recognition, radial arm maze, and spontaneous alternation). We focused on the effects of relatively short-term dietary manipulations and, therefore, restricted our analyses to studies that provided the diet for two months or less. The meta-analyses showed that each type of diet and task adversely affected performance, with the largest effect produced by exposure to a combined high fat-high sugar diet and the use of the radial arm maze to assess the effect of such diets on cognition.