Whether you have to take some time off from the gym for an injury, to cram for finals, muscle loss doesn't have to be a concern.
Increase protein intake
To maintain muscle, it is important to keep up your protein intake. A key amino acid to have here is Leucine which can be gotten from whey protein.
Stretching has been shown to increase blood flow to the muscles, increasing nutrient delivery. Stretching and increased blood flow has been shown to reduce muscle atrophy.
Keep calorie intake high
Same as protein intake. Keeping your calories high will make sure your body will not burn your muscles for fuel. You can still reduce them to take into account the reduction in physical activity. If you stay at a calorie deficit however your body will end up breaking down muscle for energy.
Supplements to reduce muscle loss
Epicatechin is an antioxidant that can hinder myostatin activity. Myostatin is a protein produced by the body to inhibit and break down muscle.
Creatine was found to be useful in slowing down both muscle and strength loss in detrained athletes