Being excessively overweight puts stress in the body and increases the risk for a number of health problems.
Nearly everyone today worries about being overweight. We're constantly inundated with messages from TV and the Internet about widespread obesity and the risks of being obese. Whether it's health issues or social acceptance, no one wants to be fat.
What is obesity?
But if you look at it from an evolutionary aspect, the ability to store excess calories in the form of fat cells is a very life-serving ability. When a person consumes more calories than the body uses for muscle movement, internal temperature maintenance and cellular repair the remainder is stored in the chemical bonds of fat cells. Technically, it's stored in something called 'adipose tissue'.
Energy - which calories measure - isn't a substance, so it's not the same as fat. But that energy becomes available for use when those fat molecules break down into simpler products. That happens when a person increases movement or otherwise triggers a need for more energy.
Carbohydrates are one major source of that energy. Sugars (chiefly glucose) and starches are the two main forms and they participate in something called the Krebs Cycle. Also known in scientific circles as the tricarboxylic acid cycle, but don't bother trying to pronounce it. Sugars come in, get broken down into something called ATP, then into ADP releasing energy in the process.
When the body runs out of glucose to use in the cycle, it turns to stored body fat as a substitute. Breaking down those fat molecules is, in essence, what causes a person to decrease the percentage of body fat. Sometimes increased muscle mass results, so the final result isn't always a net weight loss.
But in biology, as in life, everything is best in moderation. When more calories are consumed than used over a long period of time, body fat increases to the point that the health risks can outweigh the benefits of a ready supply of energy. The result is an increase in the odds of heart difficulties, diabetes and other real medical problems. The social consequences are equally well known.
Knowing this, many will strive to maintain their weight and percentage of body fat within a certain range. That range differs from person to person (people have different body types), season to season (winter fat can actually be healthy) and according to their individual BMI (Body Mass Index).
So, in order to decide whether you are obese, only moderately over the preferred weight range, or just lack muscle tone, you need to consider those factors. Doing so requires knowing your specific body type, the ability to calculate BMI (very simple, actually) and recognizing that there is no exact, static, ideal weight for you.
Common health risks from obesity
Nutrition and health science is constantly evolving, and it often seems as if the latest study contradicts earlier ones. It's hard to know what to believe. But, over the last few decades, a wide array of independent studies has tended to confirm some conclusions about the relationship between excess body fat and associated health risks.
The basic conclusion is that anyone who is considerably overweight is at higher risk for a number of potential health problems. These include various forms of heart condition, high blood pressure, diabetes, colon cancer, liver damage, gallstones and others.
But what is 'considerably overweight'?
There's no static, ideal weight for any given individual, though there are various factors that provide a healthy range. One measurement that is a good starting point is BMI (Body Mass Index). To calculate it, just divide your weight (in kg) by your height (in m) squared. The following table is a rough classification:
Under 18.5 = Underweight
Between 18.5 and 24.99 = Normal Weight
Between 25 and 29.99 = Overweight
Between 30 and 34.99 = Obese (Class 1)
Between 35 and 39.99 = Obese (Class 2)
40 and above = Extreme Obesity
For those on the lower end of the BMI scale, health risks are no more (or at most only moderately higher) than for anyone. Genetic and other environmental factors will outweigh any body fat or weight issues. But for those nearer the higher range, there is strong evidence that health risks are higher.
For example, abdominal obesity (having large fat deposits around the stomach and abdomen) is associated with increased risk of cardiovascular disease and insulin resistance syndrome. For women, a waist circumference of 35 inches or more (40+ in men) is an indicator of abdominal obesity. Among other conditions, high blood pressure, high triglycerides and high cholesterol are all common factors associated with that condition.
Narrowing of the arteries, atherosclerosis, contributes to the possibility of a clot which can cause a stroke. Excessive body fat is one factor in producing that condition. At the same time, it plays a part in increased blood pressure (hypertension).
Rapid weight gain, from 10-20 lbs for the average person, increases the odds of developing Type 2 diabetes. Genetic factors are fundamental, but weight gain plays a role, according to most studies. The risk is double that of an individual who has not had a weight gain, when other factors are held constant.
Liver disease, apart from that associated with excessive alcohol consumption, can be caused by insulin resistance. That resistance is much more likely among those who are obese. There are many studies which have correlated BMI with the degree of liver damage. The higher the BMI, the greater the odds of liver trouble.
Gallstones are more likely to form in those who are obese, and may be correlated with a rapid rise in BMI. Sleep apnea (interruption of breathing during sleep) is another condition commonly linked to obesity.
In short, though no single study is definitive, and there are many genetic and other environmental elements, excessive body fat is a substantial factor in health issues. Being overweight is not merely an issue of acceptable appearance, it's a health risk.