The Link Between Calorie Restriction and Longevity
I used to be big into bodybuilding. For anyone that’s familiar with that culture, it’s all about getting an obscene amount of calories down your throat. It does work. If you eat a lot, and lift increasingly heavier weights, you will get bigger and stronger.
I was eating around four thousand calories per day when I was looking to significantly increase mass. Yet today, at a height of six foot two inches, and a muscular two hundred pounds, I consistently eat only two thousand calories, from a maximum of two meals per day.
What’s changed? In part I wanted to focus on functional strength and mobility over pure mass. Importantly, I also would like to live longer. We all know reducing calories can help us to lose weight, but did you know that there is a growing body of evidence to suggest that it can also help us live longer?
I have previously written about the evidence backed benefits of intermittent fasting. Although the two will often intersect and overlap, it’s important not to confuse fasting with caloric restriction. Fasting relates to totally eliminating the intake of any calories for set periods of time.
Caloric restriction relates to the consistent reduction of the intake of calories below typical levels, without causing malnutrition. However, fasting can often be used to facilitate caloric restriction. Indeed, this is my approach. I fast for eighteen hours each day and consume all my two thousand calories within a six hour feeding window.
As with fasting, caloric restriction also appears to offer a wide range of health and longevity benefits. Scientists are still exploring the underlying reasons for this. But there are already a number of positive animal and human studies demonstrating why eating less may help us to live longer.
To date there are far more studies on the effects of caloric restriction on animals as opposed to humans. In many of these studies animals lived for longer, and showed far fewer instances of several diseases, especially cancers[1]. I’ll cover a few of the more prominent findings across various species.
I’ll start with a few studies on small animals, with big results. Scientist found that caloric restriction in the roundworm, had the potential to increase lifespan by forty percent[2]. A similar affect was discovered in fruit flies[3]. Studies in mice found that caloric restriction also increased lifespan, although in this case specifically due to delaying the onset of cancer as opposed to specifically slowing the aging process.
Moving up in scale to animals a little closer to humans, studies on rhesus monkeys have explored the effects in species that naturally live longer[4]. The monkeys were kept on a diet with thirty percent less calories than the control group for over twenty years. This did demonstrate an extension in life expectancy, although not to the degree in which that it did with smaller animals with naturally shorter lifespans. Other studies on monkeys also showed a reduced cancer incidence by up to as much as fifty percent[5].
Whilst the findings broadly suggest that caloric restriction extends life in a variety of species, not all studies gave positive results. In some cases, in certain species caloric restriction had no effect or even reduced lifespan[6]. However, whilst all animals are distinct from one, these studies do offer interesting insights into the potential benefits of caloric restriction in humans that are certainly worth further exploration.
There is some anecdotal evidence suggesting that caloric restriction can have positive benefits for humans. However, clinical studies are challenging due to the logistical and ethical challenges around studying humans over a prolonged period of time under acceptable conditions. And these studies would literally need to last a life time.
What can we infer from the information that is currently available? Firstly, we can turn to people like myself! Those that have taken it upon themselves to practice caloric restriction, allowing for observational studies, providing a blueprint for how caloric restriction may contribute towards longer life[7]. In particular such studies have shown the potential for reduced risk of cancer[8], diabetes[9] and heart disease[10]. The risks appear to be minimal.
However, these are observational studies and there is definitely a need for more rigorous studies in order to truly define the benefits and potential of caloric restriction. The Duke University School of Medicine undertook a revolutionary clinical trial entitled the Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy[11]. Rather a mouthful, but the acronym, CALERIE, does work very well.
CALERIE divided 218 young to middle-aged adults of average weight into two groups. A control group followed their usual diet. The other group was on a calorie restricted diet for two years, on average maintaining a twelve percent reduction in calories. This group did demonstrate reduced risk factors for diabetes, heart disease, and stroke, as well as decreased inflammation markers and thyroid hormones. Obviously this is a fairly short study, but it does offer a window of insight into the potential for caloric restriction to yield benefits in humans as well as animals.
The body of research is growing and starting to draw a clearer picture showing that caloric restriction does have the strong potential to reduce age-related diseases and extend lifespan. Scientists are conducting further research into exactly how. Some of the leading factors appear to be a reduction in inflammation, and oxidative stress, and through maintaining cellular processes, and protein structures.
There is certainly more work to be done. To date the majority of studies have been on animals and so it is not certain that these findings will apply to humans. Human studies have either been observational in nature, or rather short. They have also typically been conducted on those under sixty years of age. There is a need for longer, structured studies, and studies on the elderly. Of course this is quite a challenging undertaking.
It is also worth noting that there are a very large number of processes that keep the human body functioning and alive. We are also all very different in areas such as genetics, environment and lifestyle. So, there is a great deal more work to be done to sort through the specific inputs and outputs to fully understand the impact of caloric restriction on health and longevity, and to tweak the approach to the individual.
However, coupled with the growing body of research into intermittent fasting, there is a very strong foundation and research is ongoing on a daily basis. What if living longer could be driven by something as simple as eating less? Wouldn’t that be incredible? Then of course it would come down to a whole host of other challenges, such as will power.
What about when it comes down to integrating caloric restriction into your own life? You should make sure you’re in not likely to face any complications. However, doctors will likely tell you that there is not enough research to be able to recommend it. I can speak from personal experience. I take calculated risks with my own body and mind, with the belief that I am well informed and the rewards outweigh the risks. So, what has a couple of years of intermittent fasting and caloric restriction done to me?
As per the participants in the CALERIE study, I too have lost weight, and maintained that weight loss. Contrary to the myths of the bodybuilding community I have not totally withered away. I naturally have a strong build, and whilst not as bulky as in my bodybuilding days, I have maintained a great deal of muscle mass. I am currently sat at around two hundred pounds and twelve percent body fat. So, externally everything looks good.
What about internally? I’ve recently had a health check up and blood test. All the typical markers, such as blood pressure and cholesterol, looked great for a man in his mid-thirties. I want to know more and so I do plan to have a much more detailed blood panel done later on in the year. I will do a write up on the results. We will have to wait and see what they show, but I’m confident that they will show that I’m in superb shape!
Not all of this will be down to caloric restriction of course. I believe the sum is greater than the parts and there is no one magic pill for health, wellbeing and longevity. It’s all about the right mix. Amongst other things, my lifestyle also includes a very balanced diet, and a big emphasis on optimising my exercise, breathwork, meditation, and sleep routines. When it comes back to caloric restriction I’m a believer. At the very least it helps me with discipline, staying focused, staying lean, and ready to attack life with everything I’ve got to give it.
The Link Between Calorie Restriction and Longevity
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