However, this is not the case as many people believe that hunger and eating simply occur when energy levels in our bodies run low and that we feel full when our immediate energy levels are restored. Our body monitors its energy supplies, but this information interacts with other factors; for example, the amount and variety of food to regulate the food intake—making hunger and satiety not necessarily linked to immediate energy requirements. Moreover, homeostatic mechanisms are designed to prevent us from running low on energy in the first place. In evolutionary terms, an organism that did not eat until its energy supply started to become low (in any absolute sense) would be at a serious survival disadvantage.
Finally, many researchers believe that there is a set point; or, as said biologically, a determined standard; around which body weight (or more accurately, fat mass) is regulated. This view holds that if we tend to overeat or undereat, homeostatic mechanisms alter our energy utilization and hunger to make us return to close to our original weight. But some researchers argue that the set point theory has limitations. They propose that as we overeat or undereat, homeostatic mechanisms make it harder to keep gaining or losing weight, but do not return us to our original weight. This makes us possibly settle in a new weight over time. Stated in a different point of view, "Biology does not determine a fixed body weight but rather, a range or zone of body weight."
Genes and Environment
Some individuals gain weight more easily than others even with less consumption of foods as well as less fatty food consumption, while there are others who eat in excess with more fatty food and still stay slim for example: South Esat Asians who eat an excessive amount of fat still stay slim while others can gain weight with less amount of fat consumption. The reason for this can be in the genes, making some individuals more susceptible to gaining weight due to low metabolism, while others stay slim due to high metabolism. But there can be hormonal factors which contribute to weight gain and loss as well; such as thyroid conditions, thyroid dominance and menopause in some people. Heredity influences one's basal metabolic rate, causing a tendency to store energy as fat or lean tissue. Identical twins that are raised apart are about as similar body mass as identical twins who are raised together. This makes the genetic factors account for about 40% to 70% of the variation in BMI among both genders.
According to studies, over 200 genes have said to be have been identified as possible contributors to human obesity. However, although heredity affects our susceptibility to obesity, the environment does play a part in causing obesity too. There haven't been much changes in genes in recent decades, but the rate of obesity has had a significant increase. Experts believe the reasons to be the abundance of inexpensive foods that taste good but contain a high percentage of fats and carbs; a cultural emphasis on getting the best value, which contributes to the supersizing of menu items; and the advances in technology, which decrease the need for daily physical activity.
The Pima Indians of Arizona have provided a striking example of the way genes and environment interact in producing obesity. The Pimas have a genetic predisposition to obesity and diabetes, but before the 20th century, both these conditions were rare among the members of the tribe. Their native diet and the physically-active lifestyle prevented their genetic predisposition from expressing itself. But Pimas born after World War II, in particular, have had a dramatic increase rate in obesity with the adoption of a westernized diet and sedentary lifestyle. Today, the Pimas living in Arizona have one of the highest rates of obesity and diabetes in the world. In contrast to this, however, the Pimas living in northwest Mexico have a much lower obesity rate than their Arizona counterparts due to their sticking to a more traditional diet with more performance of physical labour.
Dieting and Weight Loss
However, for millions of overweight people, being fat primes them to stay fat, in part by altering their body chemistry and energy expenditure levels. This is an example of why obese people generally have high levels of insulin (a hormone that is secreted by the pancreas helping convert glucose into fat) than people with normal weight do. Substantial weight gain can also make it hard to exercise vigorously, and dieting slows the basal metabolism as the body responds to food deprivation with a decrease in energy expenditure.
Does this mean that diets are doomed to fail? The common adage of "Ninety-five percent of individuals who lose weight, regain the lost weight within a few years" evolved from a single study that was done decades ago. According to Albert Stunkard, one of the researchers, 100 obesity patients were given a diet and sent off, which was 'state-of-the-art' in 1959. There are no good longterm estimates of weight loss success rates in part because we rarely hear from people who succeed (or fail) on their own without the help from clinics or treatment programmes.
There are reports of around one-third of Americans trying to lose weight, although not all of them are the ones who necessarily need to lose weight. There are significant sex and ethnic differences in dieting emerging from adolescence. Some dieters are motivated by health consequences, while the primary motivators to be slim are psychological concerns and social pressures—especially among women. Which may begin as a diet may, unfortunately, evolve into a life-threatening eating disorder.
