Know the numbers. In order to lose one pound, you will need to burn 3,500 more calories than you consume in a day. How many calories you burn in a given day just by existing will depend on your current weight and level of physical activity. You can calculate this by multiplying your weight by ten.
Oxygen is crucial to sustaining life. Though it varies from person to person, on an average, 3 minutes is the maximum time where the person can stay alive without oxygen. Yoga and meditation experts may hold breath for longer than this, but these are very rare examples. In an absence of oxygen, brain cells begin to die and this effect is irreversible!
12 to 15 minutes - irreverseable brain damage intensifies and to heart as well. 15 to 20 minutes - brain damage reaches point to cease brain wave function - death. These times are estimates and can vary based on many factors however the total amount of time to death will not vary by much. Once the oxygen is depleted in the human system, biological death will occur in about 20 minutes. Hope this answers the question.