Obesity is a condition where a person has accumulated so much body fat that it might have a negative effect on their health.
If a person's bodyweight is at least 20% higher than it should be, he or she is considered obese. If your Body Mass Index (BMI) is between 25 and 29.9 you are considered overweight. If your BMI is 30 or over you are considered obese. If you're wondering what your ideal weight might be, take a look at our article, how much should I weigh?
What is Body Mass Index (BMI)?
The body mass index (BMI) is a statistical measurement derived from your height and weight. Although it is considered to be a useful way to estimate healthy body weight, it does not measure the percentage of body fat. The BMI measurement can sometimes be misleading - a muscleman may have a high BMI but have much less fat than an unfit person whose BMI is lower. However, in general, the BMI measurement can be a useful indicator for the 'average person'.
To learn more about BMI and to calculate your BMI, see our BMI article.
Why do people become obese?
People can become obese for many different reasons. Lets look at some of the most common ones:
1) Consuming too many calories.
These days people are eating much more food than in previous generations. This used to be the case just in developed nations - however, the trend has spread worldwide.
Despite billions of dollars being spent on public awareness campaigns that attempt to encourage people to eat healthily, the majority of us continue to overeat. In 1980 14% of the adult population of the USA was obese; by 2000 the figure reached 31% (The Obesity Society).
In the USA, the consumption of calories increased from 1,542 per day for women in 1971 to 1,877 per day in 2004. The figures for men were 2,450 in 1971 and 2,618 in 2004. Most people would expect this increase in calories to consist of fat - not so! Most of the increased food consumption has consisted of carbohydrates (sugars). Increased consumption of sweetened drinks has contributed significantly to the raised carbohydrate intake of most young American adults over the last three decades. The consumption of fast-foods has tripled over the same period.
Various other factors are also said to have contributed to America's increased calorie and carbohydrate intake:
- In 1984 the Reagan administration freed up advertising on sweets and fast foods for children - regulations had previously set limits.
- Agricultural policies in most of the developed world have led to much cheaper foods.
- The US Farm Bill meant that the source of processed foods came from subsidized wheat, corn and rice. Corn, wheat and rice became much cheaper than fruit and vegetables.
2) Leading a sedentary lifestyle
With the arrival of televisions, computers, video games, remote controls, washing machines, dish washers and other modern convenience devices, people are commonly are leading a much more sedentary lifestyle compared to their parents and grandparents.
Some decades ago shopping consisted of walking down the road to the high street where one could find the grocers, bakers, banks, etc. As large out-of-town supermarkets and shopping malls started to appear, people moved from using their feet to driving their cars to get their provisions. In some countries, such as the USA, dependence on the car has become so strong that many people will drive even if their destination is only half-a-mile away.
The less you move around the fewer calories you burn. However, this is not only a question of calories. Physical activity has an effect on how your hormones work, and hormones have an effect on how your body deals with food. Several studies have shown that physical activity has a beneficial effect on your insulin levels - keeping them stable. Unstable insulin levels are closely associated with weight gain.
Children who have a television in their bedroom are much more likely to be obese or overweight than kids who do not, researchers from the Pennington Biomedical Research Center in Baton Rouge, LA, reported in the American Journal of Preventive Medicine (December 2012 issue).
If you would like to know your daily calorie intake for your weight and height, take a look at our article how many calories should I eat a day?
3) Not sleeping enough
Research has suggested that if you do not sleep enough your risk of becoming obese doubles. Research was carried out at Warwick Medical School at the University of Warwick. The risk applies to both adults and children. Professor Francesco Cappuccio and team reviewed evidence in over 28,000 children and 15,000 adults. Their evidence clearly showed that sleep deprivation significantly increased obesity risk in both groups.
Professor Cappuccio said:
"The 'epidemic' of obesity is paralleled by a 'silent epidemic' of reduced sleep duration with short sleep duration linked to increased risk of obesity both in adults and in children. These trends are detectable in adults as well as in children as young as 5 years."
Professor Cappuccio explains that sleep deprivation may lead to obesity through increased appetite as a result of hormonal changes. If you do not sleep enough you produce Ghrelin, a hormone that stimulates appetite. Lack of sleep also results in your body producing less Leptin, a hormone that suppresses appetite.
4) Endocrine disruptors, such as some foods that interfere with lipid metabolism.
A team from the University of Barcelona (UB) led by Dr Juan Carlos Laguna published a study in the journal Hepatology that provides clues to the molecular mechanism through which fructose (a type of sugar) in beverages may alter lipid energy metabolism and cause fatty liver and metabolic syndrome.
Fructose is mainly metabolized in the liver, the target organ of the metabolic alterations caused by the consumption of this sugar. In this study, rats receiving fructose-containing beverages presented a pathology similar to metabolic syndrome, which in the short term causes lipid accumulation (hypertriglyceridemia) and fatty liver, and eventually leads to hypertension, resistance to insulin, diabetes and obesity.
Poorly balanced diets and the lack of physical exercise are key factors in the increase of obesity and other metabolic diseases in modern societies. In epidemiological studies in humans, the effect of the intake of fructose-sweetened beverages also seems to be more intense in women. (From - "New Data On Fructose-Sweetened Beverages And Hepatic Metabolism").
Although there appears to be a consensus on the negative effects of fructose-sweetened beverages there is still some debate over the effects of fructose versus high fructose corn syrup - two studies of note are:
- AMA Finds High Fructose Syrup Unlikely To Be More Harmful To Health Than Other Caloric Sweeteners
- Fructose Sweetened Drinks Increase Nonfasting Triglycerides In Obese Adults
Fructose effect on the brain may promote obesity - researchers from Yale University School of Medicine compared the effects of fructose and glucose on the brain with MRI scans and found that high fructose diets may be behind the current obesity epidemic.
In an article published in JAMA (Journal of the American Medical Association), the authors said they found that regions in the brain that regulate appetite became active when people consumed glucose, but remained inactive when they ingested fructose. When those regions become active, they release hormones that produce feelings of satiety (fullness) - in other words, the hormones tell you to stop eating.
5) Lower rates of smoking (smoking suppresses appetite)
According to the National Institutes of Health (NIH) "Not everyone gains weight when they stop smoking. Among people who do, the average weight gain is between 6 and 8 pounds. Roughly 10 percent of people who stop smoking gain a large amount of weight - 30 pounds or more."
6) Medications that make patients put on weight
According to an article in Annals of Pharmacotherapy, some medications cause weight gain. "Clinically significant weight gain is associated with some commonly prescribed medicines. There is wide interindividual variation in response and variation of the degree of weight gain within drug classes. Where possible, alternative therapy should be selected, especially for individuals predisposed to overweight and obesity." (The Annals of Pharmacotherapy: Vol. 39, No. 12, pp. 2046-2054. DOI 10.1345/aph.1G33)
7) Is obesity self-perpetuating?
The longer a person is overweight, the harder it becomes for them to lose weight. Many have wondered whether obesity itself becomes a permanent state, i.e. does obesity promote obesity?. Researchers from the University of Michigan and the National Council of Science and Technology (COINCET) in Argentina, reported in the Journal of Clinical Investigation that in animal experiments, obesity seems to become a self-perpetuating state.
They found that the “normal” body weight of mice that become obese starts going up; their bodies’ perception of normal weight becomes a heavier than before, regardless of whether they are made to go on diets which had made them lose weight.
Senior author, Malcolm J. Low, M.D., Ph.D., said "Our model demonstrates that obesity is in part a self-perpetuating disorder and the results further emphasize the importance of early intervention in childhood to try to prevent the condition whose effects can last a lifetime. Our new animal model will be used in pinpointing the reasons why most adults find it exceedingly difficult to maintain meaningful weight loss from dieting and exercise alone."
In addition to this study, research published in the journal Nature Communications in 2015 suggests that weight loss is harder when we carry more fat. The scientists suggest that the more fat we carry, the more our bodies appear to produce a protein that blocks our ability to burn fat.
8) Obesity gene
A faulty gene, called FTO, makes 1 in every 6 people overeat, a team of scientists from University College London reported in the Journal of Clinical Investigation (July 2013 issue).
Lead researcher, Racher Batterham, explained that people who carry the FTO gene variant tend to eat too much, prefer high-energy, fatty foods, and are usually obese. They also appear to take much longer to reach satiety (feeling of being full).
Follow us to the next page where we take a look at the available treatments for obesity.