Surprisingly enough, you: Gain water weight, Lose focus, Your energy levels drop, You can get crankier, Your risk for a stroke becomes higher, You feel hungrier, Your metabolism becomes slower, You may get headaches, Your skin worsens (acne, dry skin, etc), Your workout performance suffers, You stop crying, (For men) Occasionally there are cases of erectile dysfunction, Your pee changes color, You have trouble going to the bathroom, Your kidneys will tank, And your heart will tank as well.
You should shelter in place under these circumstances. Your office is a safe enough environment that you would encounter more hazards by leaving rather than sheltering in place.
The basis for physical fitness is having a good eating habit, which means to know what you are eating and to eat cleanly. Exercise at least an hour every day and drink plenty of water throughout the day.