Not only people become thicker, but also animals that live near a person, not only pets, but also monkeys, rodents, wild rats. Scientists from the University of Alabama (USA) suggest that certain environmental factors, such as infection or artificial lighting, and not just food and lack of mobility, can lead to the spread of obesity.

"It may be something that is in the air, in water or in food, but not the food itself," says David Allison, lead author of the study.

According to scientists, viruses or other pathogenic organisms, or some chemicals, make people and animals gain weight. As possible factors, scientists call adenovirus type 36, which causes weight gain in animals, dioxins that disrupt hormonal balance, conditioners or central heating.

After analyzing the available data on 20,000 animals collected in recent decades, the researchers concluded that the parallel increase in weight in humans and animals can not be explained solely by caloric intake and lack of movement. Animals belonged to different species, and their diet and way of life were also completely different.

Scientists have studied cats, dogs, wild rats, laboratory rodents and laboratory primates of four different types, including chimpanzees.

Weight gain in domestic cats and dogs can be explained by diet and lifestyle - probably now they eat more calorie foods, and move less than their ancestors. But this does not explain why the thicker, for example, rodents from the American national toxicological program.

The general tendency of weight gain in recent decades has been traced in all animals, regardless of their physical activity or nutrition.

"The coincidence of the results in different animals living in different conditions, including those whose diet has been tightly controlled and not changed for decades, makes it possible to assume that weight gain is associated with some unknown or poorly studied factor," scientists conclude..

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