**1. Introduction**

Living organisms are constitutionally wired to store energy for survival in periods of scarcity. Eel and salmon are reported to survive long periods without food [1–3]. The excess intake of calories leads to energy accumulation in the form of fat, glycogen, or starch. Plants store energy reserves as starch and oil. We were unable to find reports of adverse consequences of excess energy storage in plants and lower organisms. The stored energy helps the organism to tide over periods of calorie scarcity and during hibernation, aestivation, or migration in animals. In higher organisms, deposition of excess calories results in impairment of body functions with adverse



### **Table 1.**

*Multiple consequences of obesity.*

effects on health and longevity. Obesity with adverse health effects has been reported in zebrafish [4], reptiles [5, 6], and birds [7].

Energy in humans is stored as glycogen or triacylglycerols (TAGs). Relative to the amount of calories that can be stored as triacylglycerols (TAGs), only a small amount of calories can be stored as glycogen. An adult liver can store up to 120 g glycogen, while the skeletal muscles can store up to 400 g glycogen. Triacylglycerols are hydrophobic energy-dense molecules that can be stored in large amounts in the adipocytes. Adipose tissue is the loose collection of adipocytes in a mesh of collagen fibers, deposited at various sites in the body. Preadipocytes, fibroblasts, vascular endothelial cells, adipose tissue macrophages, and small blood vessels are also present in the adipose tissue.

Increased mass of adipose tissue, abnormal site of deposition, or abnormal size of adipocytes can result in adverse consequences on health and quality of life (**Table 1**).
