In 1935, researchers conducted the first study on the effects of calorie restriction. The study used rats, and they found that restricting daily caloric intake actually increased the rats’ lifespan.
Since that time, further studies have revealed similar results in the lifespan of yeast, worms, flies, rodents and monkeys. In primates, the effects of calorie restriction were even more profound, leading to reduced risk of age-related diseases like diabetes, heart disease, cancer and dementia.
The connection between calorie restriction and lifespan is less clear in humans, though, so researchers in Denver conducted a review to see what, if anything, existing studies have shown.
There are several different ways to create a calorie deficit:
- Calorie restriction (simply eating fewer calories);
- Alternate day fasting (alternating every other day between fasting and eating whatever desired);
- A combination of restricting food intake and exercising; and
- Restricting specific groups of food.
For this study, researchers focused specifically on calorie restriction alone and how it affected humans.
In looking at people who partake in religious fasting, researchers noticed that the Greek Orthodox, who eat a nearly vegetarian diet for 180 to 200 days every year, had lower body mass index (BMI), total cholesterol and LDL cholesterol during post-fast times as compared to pre-fast times.
They also looked at people who follow The Daniel Fast — a vegan diet for 21 to 40 days. After 21 days, these people had improved total cholesterol, LDL cholesterol, blood pressure, insulin and C-reactive protein levels.
Next, researchers examined the lifestyles of people who lived on the Japanese islandof Okinawa, who have a life expectancy among the highest in the world. They found that, in the elderly Okinawans, “there had been a lower caloric intake and negative energy balance in earlier life with a resultant life-long low BMI, decreased risk for age-related disease, and an extended life span versus mainland Japanese and Americans.”
Finally, in a current ongoing study of calorie restriction called the Comprehensive Assessment of the Longer Term Effects of Reducing Intake of Energy (CALERIE), researchers have so far noticed lower body weight, decreased whole body and visceral (belly/abdominal) fat, and improved fasting insulin levels and cardiovascular markers (such as cholesterol and C-reactive protein).
While all of these improved health markers are wonderful news, the jury is still out on whether or not calorie restriction actually helps to prolong human life. However, you can deduce that improved health and health markers, such as those witnessed in these studies, could probably lead to a longer life.
How Many Calories Should You Cut?
According to researchers, people who practice calorie restriction usually eat about 25 percent fewer calories than recommended, and what they do eat is extremely nutrient-dense and filling.
The average daily recommendation is 2,000 calories per day for women and 2,500 calories per day for men. Reducing that by a quarter would mean 1,500 calories for women and 1,875 for men.
If this seems like too much for you to cut but you still want to restrict calories to improve your health, then try reducing your average daily intake by 200 or 300 calories, or as much as you feel comfortable cutting.
Researchers did acknowledge that most people who practice strict calorie restriction are not able to stick with it. They don’t state a reason why, but it doesn’t take a rocket scientist to figure out that it’s probably because they either end up too hungry or give in to temptation.
Those who successfully practice calorie restriction are able to do so well because they eat healthy foods that allow them to stay fuller longer. The key is to make whole grains, vegetables, fruits and lean protein like eggs, fish and chicken your diet staples. Some wonderfully delicious and filling whole grains include quinoa, amaranth, buckwheat and millet.
Strict calorie restriction may work for some people, but may be too difficult for others to maintain. If straight calorie restriction is too radical of an approach for you to follow but you still want to lose weight or improve your health, do what doctors recommend most often: Eat a nutritious, balanced diet and exercise.
Even if you eat 2,000-2,500 calories in a day, exercise will burn significantly more of those calories than sitting around will, so you automatically create the calorie reduction necessary to lose weight and improve your health.
The bottom line: No matter what your approach, the end result is better health, and that should be everyone’s ultimate goal!
 Roth L and Polotsky A. Can we live longer by eating less? A review of caloric restriction and longevity. Maturitas. 2012 Apr;71(4):315–19.
 Willcox BJ, Willcox DC, Todoriki H, et al. Caloric restriction, the traditional Okinawan diet, and healthy aging: the diet of the world’s longest-lived people and its potential impact on morbidity and life span. Ann NY Acad Sci. 2007 Oct;1114:434–55.