Obesity can affect life expectancy rates in humans and their pets. Up to eight years of someone's life expectancy could be taken away by obesity, according to research.

Recent data shows that humans have been increasing in size over the years, as well as dogs, cats and horses.

A study published on Britain's premiere medical journal said that being extremely overweight could shorten a person's healthiness by 19 years. Young people are at the greatest risk.

A research team analyzed the effects of obesity and overweight through a computer model.

Dr. Steven Grover, leader of the research team, said "Our computer modeling shows that obesity is associated with an increased risk of developing cardiovascular disease and diabetes that will, on average, dramatically reduce an individual's life expectancy," according to the BBC.

Economic factors can contribute to what families eat and how they feed their pets.

"There is something about our shared environment that is generating obesity in both humans and our companion animals," Professor David Raubenheimer, a nutritional ecologist at the University of Sydney's Charles Perkins Centre, told the Daily Mail.

"If it's more expensive to buy protein balanced foods for ourselves, imagine economically stressed families' response when they feed their pets," he said.

Today, cats are 25 percent larger than they were 10 years ago while dogs increased in size by 33 percent.

Meanwhile, the National Cancer Institute conducted a study that found extreme obesity can reduce life expectancy by up to 14 years.

"While once a relatively uncommon condition, the prevalence of class III, or extreme, obesity is on the rise," said Cari Kitahara, Ph.D., Division of Cancer Epidemiology and Genetics, NCI and lead author of the study.

Dr. Kitahara found that, in the United States, six percent of adults are now classified as extremely obese, which, for a person of average height, is more than 100 pounds over the recommended range for normal weight.

Nutrition researcher Margaret Allman-Farinelli said that the early years of adulthood are the most dangerous time to gain a lot of weight.