Tolerance to any substance is typically caused by repetitive or long-term use. This happens because the receptors for caffeine in the body can get “used to it.’ This is due in part to the body’s ability to adapt and maintain balance, or homeostasis.
When this happens, one cup of coffee won’t wake you up as well as it did the day before. Instead, you’ll need an extra shot of espresso or cup of coffee just to get the same effect. Over the weeks and months, you may find yourself drinking 4, 5, or more cups of coffee but still end up feeling sleepy.
Another factor that can cause energy crashes
Aside from copious amounts of caffeine, beverages like coffee, soda, and energy drinks can contain a lot of sugar. Typically, the type of sugar that is in these sweetened beverages are simple sugars like fructose.
The benefit of simple sugars is that it is quickly available for use by the brain and other organs. On the other hand, this extra sugar ends up stored as fat in the body. The sugar rush provided by sodas and energy drinks gives energy to the brain while caffeine makes the brain work more quickly.
After the initial sugar rush, an energy crash can happen. This is also known as reactive hypoglycemia. The body responds to the excess sugar in the blood by releasing large amounts of insulin, causing a spike. Insulin signals the liver to store extra sugar as glycogen, and the fat and muscle cells to take up glucose.
Because the body suddenly releases a lot of insulin into the blood, too much sugar can be taken out of the circulation. The sugar and caffeine crash symptoms include: