A paper from The Endocrine Society lists a few of the most common factors:
Imbalance of the body’s energy systems. Minor weight loss can slow the metabolism, leading to reduced energy expenditure even during exercise. However, it can also increase hunger, causing you to eat more. With less energy burned and a higher calorie intake, you’ve got the ideal conditions for weight gain—exactly the opposite of what you wanted.
Genetics. There are many genetic factors that play a role in our modern obesity epidemic. People can pass on their propensity for obesity, heart disease, diabetes, and other problems to their children. Though not all genetic factors have been identified, it is well-documented that genes can play a role in obesity and weight loss difficulties.
Environment. Given our low-activity lifestyles and our food-promoting environment, we’re already at a disadvantage before we even begin trying to lose weight.
Endocrine-disrupting chemicals. Chemicals like Bisphenol-A (BPA) can disrupt the delicate endocrine balance in the body, leading to a higher risk of weight gain and obesity.
Diet composition. Our modern diet is heavy in carbs, many of which contain little nutritional value for all the calories. Thankfully, healthy fats are once again becoming common on the menu, so we’re encouraging our bodies to adapt to be more fat-burning than they once were.
Gut bacteria. The more research that’s done into the gut microbiomes, the more we understand how important the bacteria is for our health overall. Gut bacteria play a role in everything from cognitive function to immune health, and obesity/weight gain/loss is definitely one of the factors affecting and affected by our weight loss efforts.
So, we can be certain that, sadly, there is no diet, exercise, prescription, or surgery, that will change the way the body conforms to its perceived norms, generally the highest weight it has been over time. Which is why the long-term it is so bloody hard to lose weight. Delving into neurobiological solutions has to be part of a longer term solution for anyone dealing with obesity.
As the authors of the study say, “The identification of neuromolecular mechanisms that integrate short-term and long-term control of feeding behavior, such that calorie intake precisely matches energy expenditure over long time intervals, will almost certainly enable better preventive and therapeutic approaches to obesity.”
1. Michael W. Schwartz, Randy J. Seeley, Lori M. Zeltser, Adam Drewnowski, Eric Ravussin, Leanne M. Redman, Rudolph L. Leibel. “Obesity Pathogenesis: An Endocrine Society Scientific Statement.” Endocrine Reviews, 2017.