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Low-carbohydrate, ketogenic diets (KD) are frequently implemented in efforts to reduce or maintain body weight, although the metabolic effects of long-term exposure to this type of diet remain controversial. This study assessed the responsivity to peripheral and central insulin, glucose tolerance, and meal-induced effects of consuming a KD in the rat. After 8 wk of consuming chow or KD, caloric intake after peripheral or central insulin and insulin and glucose levels after a glucose challenge were assessed. In a separate group of rats, glucose and insulin responses to either a low- or high-carbohydrate test meal were measured. Finally, rats maintained on KD were switched back to a chow diet, and insulin sensitivity and glucose tolerance were evaluated to determine whether the effects of KD were reversible. Maintenance on KD resulted in decreased sensitivity to peripheral insulin and impaired glucose tolerance. Furthermore, consumption of a high-carbohydrate meal in rats that habitually consumed KD induced significantly greater insulin and glucose levels for an extended period of time, as compared with chow-fed controls. Responsivity to central insulin was heightened in KD rats and associated with increased expression levels of insulin receptor mRNA. Finally, returning to a chow diet rapidly reversed the effects of KD on insulin sensitivity and glucose tolerance. These data suggest that maintenance on KD negatively affects glucose homeostasis, an effect that is rapidly reversed upon cessation of the diet.
Here you go: this is a much better study. Clearly not “pro-KD” by any means. (This is 2010, the pro-KD camp would be a very tiny minority at this point.) The authors still seem to believe there is something bad about the effects of the KD, but at least they looked into and found that these “negative” effects were “rapidly reversed upon cessation of the diet”.
Again, Virta Health’s success reversing T2D using KD as well as studies showing increased average lifespan of mice fed a KD – as long as they were not allowed to become obese eating it – indicate the effect described are not ultimately harmful.