Lower caloric intake increases longevity - the CALERIE study

The CALERIE study tested if a longer restriction in caloric intake can prolong one's lifespan. It stands for the Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy, and the second and main phase started in 2007 and lasted until 2010. 

Keep reading and discover what the CALORIE study learned about extending our lives through lower calorie intake. 

Why was the CALERIE study conducted?

Multiple studies that were done on animal models showed that calorie restriction extends lifespan and prevents the development of age-related chronic diseases. This was shown in animals like mice and rats, insects, and even rhesus monkeys (1). Findings like these prompted similar studies on humans. 

The CALERIE study had a shorter phase I with fewer participants in 2006 (2). Phase I was done with 48 participants for six months, and the results showed that the treated group (ate 25% less calories) had lower:

• insulin resistance,
• lower level of LDL cholesterol,
• body temperature,
• blood insulin levels,
• oxidative damage to DNA. 

These conclusions were considered exceptionally positive and they pushed toward expanding the study and conducting phase II. 

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How was the study designed?

The second of the two phases of the CALORIE study was bigger and longer. It was conducted from May 8, 2007 until February 26th, 2010. In total, it had 238 participants, which had to be young and not obese. To be eligible to participate in this study, you had to:

• have a BMI of 22 - 27.9,
• be a non-smoker,
• be a non-diabetic,
• be up to 47 (for women) or 50 (for men) years of age,
• be generally healthy. 

The study was randomized into two groups, those who were on a 25% calorie restriction diet and those who consumed a standard diet. 

The important aspect of the calorie-restricted diet was that it wasn't deficient in any nutrient, only in calories (3). 

Regular check-ups were scheduled for every month of the study, and the following aspects were monitored:

• blood pressure,
• heart rate,
• core temperature,
• waist measurements,
• body composition and bone mineral density,
• resting metabolic rate,
• oral glucose tolerance test,
• muscle strength testing,
• immune function testing. 

You can read more about the study's design and other specifics here. 

What were the results?

Much like phase I of this study, the bigger phase II had similar positive findings. In young, healthy participants, caloric deficit significantly reduced the risks of developing cardiovascular diseases. 

More specifically, all usual cardiovascular risk factors were reduced, such as:

• LDL-cholesterol
• total cholesterol to HDL-cholesterol ratio,
• systolic and diastolic blood pressure,
• C-reactive protein,
• insulin sensitivity.

Even the factor of DNA aging, methylation, was significantly improved. During the two years of the study, participants who were on a calorie-restrictive diet also lost 7.5 kilograms on average, after holding an average restriction of 11.9% fewer eaten calories. 

Should I eat less to live longer?

In short, the calorie-restriction diet produced some interesting and beneficial results over two years, but it may not be for everyone.

It should be controlled and calculated exactly how many calories you need per day, because you may already be in a caloric deficit. Eating even less than that could be dangerous, and you may risk not eating enough nutrients. Therefore, such a diet should be designed by a professional nutritionist or after consultations with your health providers. 

In general, eating fewer calories seems to have a very positive effect on our bodies. It can help us have better heart health and quality of life in older age. 

 Literature:

1. Eat less, live more. (2006) The Economist. 
2. Waziry R, Ryan CP, Corcoran DL, Huffman KM, Kobor MS, Kothari M, Graf GH, Kraus VB, Kraus WE, Lin DTS, Pieper CF, Ramaker ME, Bhapkar M, Das SK, Ferrucci L, Hastings WJ, Kebbe M, Parker DC, Racette SB, Shalev I, Schilling B, Belsky DW. Effect of long-term caloric restriction on DNA methylation measures of biological aging in healthy adults from the CALERIE trial. Nat Aging. 2023 Mar;3(3):248-257. doi: 10.1038/s43587-022-00357-y. 
3. Mattison JA, Roth GS, Beasley TM, Tilmont EM, Handy AM, Herbert RL, Longo DL, Allison DB, Young JE, Bryant M, Barnard D, Ward WF, Qi W, Ingram DK, de Cabo R. Impact of caloric restriction on health and survival in rhesus monkeys from the NIA study. Nature. 2012 Sep 13;489(7415):318-21. doi: 10.1038/nature11432.