If you are a meat eater, you are less likely to suffer from zinc deficiency as meats are one of the best foods rich in zinc. The meats that have the highest concentration of zinc include beef, lamb, pork, chicken and turkey. A 100 gram serving of cooked lean beef contains 12.3 mg or 82% DV of zinc.
Endothermic reactions absorb energy from the surroundings, while exothermic reactions release energy to the surroundings. Fuels release energy when they burn. The energy output of a fuel can be measured by calorimetry using a known mass of water.
In this sense, all reactions absorb energy before they begin, but the exothermic reactions release even more energy. This can be explained with a graph of potential energy: This graph shows an exothermic reaction because the products are at a lower energy than the reactants (so heat has been released).