India, Oct. 4 -- A sleepless night might leave you groggy, but missing sleep for a few days can affect your body in surprising ways. From your metabolism to your mood, lack of rest can have serious effects. In his September 25 Instagram post, fitness coach Yash Vardhan Swami breaks down exactly what happens when you don't sleep well for 1-4 days. (Also read: Fitness coach shares top 5 'supplements' that can actually help you lose weight and boost health: 'If you sweat a lot.' )

Day 1: Swami points out that after a single night of poor sleep, your reaction time can drop by 25 percent, which is comparable to being legally drunk.

Day 2: "Two days of poor sleep can reduce your working memory by up to 35 percent, slowing down decision-making...