There was a significant positive correlation between leptin and lipids and a significant negative correlation between ketone bodies and glucose.

瘦素水平与血脂水平呈极显著正相关，血酮与血糖呈极显著负相关。

Because there is no more glucose and the fats are too large to cross the blood-brain barrier, your brain changes modes and begins to use ketone bodies for energy.

因为已经没有葡萄糖了而脂肪又太大无法穿过血脑屏障于是大脑改变模式开始用酮类产生能量。