Do Fewer Calories Mean A Longer Life?

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Most people understand the importance of calories with regard to bodyweight. The more you take in, the more weight you will gain unless you are leading a physically active lifestyle. But not many people would think that the number of calories they take in on a daily basis could affect not only their waistlines, but their lifespan as well. According to some research, there is indeed a connection, and those who recognize it and adjust their lifestyles accordingly could not only have healthier lives, but longer ones as well.

But is this really the case? In the endless battle of science, some experts are now claiming what works on animals may not work for humans. Let’s get to the bottom of this mystery and find out what’s really going on.


The Connection Between Calories, Metabolism and Your Biological Clock.

Have you ever experienced a mid-afternoon dip in your energy levels? This is due to the natural progression of you circadian rhythm, a cycle in your body that regulates when you fall asleep and wake up, and when you experience increases and decreases in energy. It turns out that as you age, your circadian rhythm changes over time as part of the natural process of getting older.  Your cells’ ability to efficiently metabolize energy can actually influence your circadian rhythm and your aging process as well.

A team of researchers at the University of California at Irvine wanted to determine exactly how much of a role age plays with metabolism and how this relates to the lifespan of the mice. They did this by taking tissue samples from the livers of mice at the age of six months, and then again when the mice had reached 18 months. They chose the liver because it plays a key role in nutrition and the process of changing food molecules into energy. The metabolic process is heavily influenced by the circadian rhythm. There were no changes in the quality or type of food the mice were given during this time.

They found that the older mice were not able to metabolize energy as efficiently. However, when they compared the results from these mice to a separate group that was fed 30 percent fewer calories per day over a six-month period, they found an interesting difference: The mice eating fewer calories experienced no decline in metabolic efficiency.


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According to Paulo Sassone-Corsi, who led the study, they had effectively “rejuvenated the biological clock” of these older mice by not requiring their cells to work as hard, because they did not have to metabolize so many calories.

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Lifespan and Caloric Restriction.

A review of relevant scientific literature published in the American Journal of Clinical Nutrition concluded that restricting caloric intake had a beneficial effect on the health of a variety of test animals ranging from mice, rats, fish, worms, and even yeast. Experiments performed on animals that are more similar to humans yielded similar results.

Researchers at the National Institute on Aging and the University of Wisconsin-Madison conducted a long-term caloric restriction experiment on rhesus monkeys, a primate that exhibits physiological aging patterns quite similar to those of humans. (Interestingly, they also followed the 30 percent calorie reduction approach used in other experiments.) One of the monkeys followed this reduced calorie diet from the age of 16 years onward. As of 2016, this monkey was 43 years old — a remarkably long lifespan for a rhesus monkey. According to a report on the experiment in Scientific American, it would be the equivalent of a human living to be 130 years old.

But will such an approach result in drastically extended lifespans for humans who adopt it? According to the same article in Scientific American, it might not.

There are many more factors at work in a human lifestyle versus the lifestyle of an animal. Some humans are athletic or work in very physically demanding jobs. Others are very obese and live sedentary lifestyles. Should they be following the same restricted diet?

Probably not. The physically active person most likely needs those extra calories to provide energy for a body that performs at a higher level than normal.


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Calories also are not created equal, so the source of the calories is a huge factor. A thousand calories in the form of a fast food meal is very different than the same amount in nuts, fish, and fresh vegetables. Eating a lot of good calories is better than eating a small number from junk food.

Recent research has found that following a restricted calorie diet for up to five days per month might represent a reasonable middle ground and could indeed lead to better health and possibly a longer life in the long run. On the other hand, consistent, nonstop, severe caloric restriction in humans could actually lead to nutrient deficiencies.

More research needs to be done, but as it stands now, the long-term effects of caloric restriction are not fully understood. It is probably better to just follow a healthy lifestyle of eating good, nutritious food and being physically active as much as possible.