Studying metabolism in primates, scientists have found two very interesting things that can be interpreted as good and bad news. The good news is that the slow compared to other mammals metabolism in humans provides for a long life span. The bad news is that it is impossible in principle to lose weight with the help of physical exercise.
A year ago, scientists expressed doubt regarding a seeming truism that active lifestyle contributes to weight loss. An international group of anthropologists observed hunters from an African tribe Hadza who do not sit still for a minute. The observations showed that they burnt the same amount of calories a day as sedentary Europeans. Thus the scientists made an assumption that jogging, gyms and such do not promote weight loss.
Recently, this assumption was confirmed by a group of zoologists led by Dr. Herman Pontzer with Hunter College of New York (USA). However, scientists have approached this issue from a different angle. They were interested whether there was a connection between the fact what primates have the slowest metabolism among mammals and their longevity and late onset of puberty. First they had to determine whether the metabolism of our closest relatives was indeed slow of whether it was typical only for some specific people and monkeys and was not a general rule for all primates.
The researchers conducted a number of experiments in which energy consumption was estimated in 17 primate species. The sample size was rather broad and ranged from tiny mouse lemurs to massive gorillas, and involved both adults and young subjects. Non-invasive methods were used, i.e., those that did not require direct penetration into the animals' bodies. For example, one method was to measure the amount of carbon dioxide emitted by the monkeys. The data obtained were then compared with other similar studies concerning both primates and other mammals.
The result revealed an interesting detail - all primates indeed burn 50 percent fewer calories than other animals. This has nothing to do with age. For example, baby gorillas burn 50 percent fewer calories than a puppy or a kitten of the same age. Most likely, the relationship between the rate of aging and the intensity of metabolism does exist, and economical metabolism explains the slow rhythm of life of primates as rapid development and frequent reproduction require large amounts of energy and, in addition, active energy burning accelerates aging.
However, there is one negative effect, and slow metabolism does not allow primates to have many children compared to rabbits or rodents. On the other hand, it is not that bad because a small number of offspring would ensure that more energy is spent on their training. Thus, it can be concluded that a slow metabolism can be considered an evolutionary trend, and that primates made a bet on it from the very beginning of their existence. The fact that one of the species of this group became the dominant living being on planet Earth says that this evolutionary "choice" was correct.
The research has revealed another very interesting detail. The reported energy consumption in primates in captivity was about the same as in their relatives who still live in the wild. Yet, in a zoo or a vivarium monkeys move five times less than the inhabitants of the jungle and savanna. This implies only one thing - physical activity of primates does not affect their calories burning process. Simply put, a monkey may lie all day in a hammock or jump from one tree branch to another, scaring all the inhabitants of the jungle with their screams, but from the energy point of view the result will be the same.
It also raises the issue of advising overweight patients to exercise. Would this help if we know that primates with sedentary lifestyle in zoos spend as much energy as those that live in reserves? Humans are also primates and many physiological patterns in this group apply to us. Examples of dogs and cats that lose weight with exercise are incorrect as their metabolism is much faster than ours. A person who is trying to lose weight by running would have to run a marathon every day in order to catch up in energy spending with any non- primate close in size (e.g., Caucasian Shepherd).
However, this does not mean physical exercise should be ignored. It does have a positive impact on health, for example, it strengthens circulatory, respiratory, and nervous systems. On the other hand, we should not expect that regular jogging or fitness classes would lead to the desired weight loss.
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