Calorie restriction (CR) is a strategy - a lifestyle choice when practiced by humans - proven to extend healthy and maximum life span in rodents and primates. Some animal studies conducted over the past 20 years have shown up to a 40% increase in maximum life span. CR also provides numerous secondary health benefits, such as a greatly lowered risk for most degenerative conditions of aging. Recent studies have demonstrated these same secondary health benefits in humans. Many researchers believe the evidence to date shows the practice of CR will extend the healthy human life span, but consensus has not yet been reached on this topic.

Calorie Restriction in a Nutshell A calorie restriction diet aims to reduce your intake of calories to a level 20-40% lower than is typical, while still obtaining all the necessary nutrients and vitamins. CR is also known as CRON, for "calorie restriction with optimal nutrition." Mild CR may be as easy as adopting a much healthier diet, taking a few supplements and not eating snacks.

The degree to which CR can extend the healthy human life span is open to debate - and is the subject of vigorous discussion within the scientific community - but the evidence for at least some healthy life extension is compelling. A sampler of articles from the past few years illustrates this point:

Impressive Calorie Restriction Statistics The Evidence For Calorie Restriction CR Reduces DNA Damage CR Beneficial Late in Life Calorie Restriction Cleans Cells CR Enhances DNA Repair

Study Backs Human Calorie Restriction CR Protects Against Heart Aging CR Slows Immune System Aging CR Slows Alzheimer's Progression CR Reduces Stem Cell Decline CR Reduces Inflammation and Muscle Loss

Modern CR Science The beneficial effects of CR in laboratory animals have been known for a long time, but only in the past decade - and in particular over the past few years - has more funding and effort been devoted to this field. In the present day, human studies such as CALERIE are underway and many research groups are digging into the biochemistry that could explain how and why CR is so good for health and longevity. The genes and processes that control metabolism are notoriously complex, and scientists do not yet have a complete understanding of the way in which CR fits into the overall picture. But they are working on it.

Before going further, it is a good idea to read the Longevity Meme disclaimer and take a few moments to think about responsibility and health. It is a wise idea to consult with your physician before embarking on any change in diet aimed at improving your health or longevity, especially if you have a medical condition. There is no substitute for taking personal responsibility in health and research! That said, on with the discussion of calorie restriction. You may have seen CR mentioned more often and in more detail in the mainstream media of late; the phrase "low-calorie diet" has also seen a lot of usage. To be precise about these terms, calorie restriction is simply the most widespread and well-researched form of low-calorie diet. You can find out more about the science and technical details of calorie restriction here at the Longevity Meme: Calorie Restriction, Lifestyle and Diet articles

Many reputable health websites maintain an informative section on CR. InfoAging, funded by the American Federation for Aging Research (AFAR), is one of the more useful of these resources:

• Read About CR At InfoAging

Unfortunately, some of these resources exaggerate minor difficulties experienced by people who practice CR - this is something you will see in the media as well. An article from MSNBC in early 2003 went so far as to use the word "torturous" to describe the experience of trying CR! This is all far from true: starting on CR is no harder than any other diet change.

Weight loss should be mentioned in the context of CR, even though it is not the primary goal of a CR diet - if you eat fewer calories, you will slim down. Research indicates that being overweight, or carrying excess body fat, is harmful to your long term health in many different ways. Excess weight increases risk factors for conditions ranging from diabetes to cancer to Alzheimer's, most likely due to the relationship between fat cells and chronic inflammation. It is no exaggeration to say that if you are overweight, you will have a shorter, less healthy life - many recent studies suggest that even comparatively little excess weight is bad for you over the long term, significantly raising your chances of suffering a range of age-related conditions. Some portion of the health benefits of CR are likely to stem from the accompanying loss of weight and body fat - although biochemical research indicates that there is clearly more than just that going on under the hood. CR is also doing something positive with the controlling mechanisms of metabolism.

For example, it appears that CR provides a boost to the process of autophagy. Autophagy is the way in which your cells remove damaged components in order to recycle the materials into new replacement parts. Several lines of research indicate specific types of damaged cellular components left to cause problems over time contribute to age-related decline and damage inflicted upon the rest of your body's machinery.

How to get started on CR? You'll find a wealth of information and many, many starting points out there, some of which can be quite intimidating to the newcomer. You might find the following path useful:

Obtain a Copy of "The Longevity Diet: Discover Calorie Restriction"

This book is a very good, easy introduction to the principles and simple ideas behind calorie restriction. Beyond that, it is a practical guide that will help you over a lot of the early pitfalls. It handily answers the "what exactly is it I eat?" question and offers some great tips for new practitioners.

• The Longevity Diet Website

Practice Eating a Better Diet First

While you're waiting for your book to arrive, you can start to shift your diet in preparation. Have a look at this resource for a class of diets known as "Paleodiets":

• Investigating Paleodiets

The selling point of Paleodiets is that they replicate the hunter/gatherer diet of our ancestors, and are therefore better for us. This is not an argument advocated by the Longevity Meme at all, but Paleodiets make a great introduction into calorie restriction.

One thing you'll find out quite early on in your journey into calorie restriction is that you'll have to stop eating a lot of highly processed, rich, modern foods. They are heavy in calories and light in nutritional value. In the US, you can walk into any corner store and eat 1500 Kcal of junk food (chips, chocolate, and so forth) at a cost of $10. You'll be hungry again a few hours later. That same $10 could feed you for two days if you buy vegetables, rice and tofu. You could eat 1500 Kcal a day and hardly be hungry at all.

These two examples are at the opposite ends of the spectrum, but most people eat far more rich food and many more "empty calories" (calories that do not provide vitamins and essential micronutrients) than they should. Adopting a Paleodiet for a while is an easy way to start thinking seriously about what you eat, how you cook, and how you can better organize your eating habits. It's a smaller and more manageable jump than leaping straight into calorie restriction.

If you were eating an unhealthy diet before trying this, you'll probably notice the benefits of healthy eating within a few weeks. Your palate will become more sensitive to subtle tastes, you'll need less sleep, feel more alert, and mood swings will be diminished. Much of this stems from cutting processed sugars.

Pay Attention to Calories

Counting calories is a good thing, and it's something that you have to pay attention to. Your body will let you eat far more than is good for you, so your brain is going to have to take over managing the process.

Almost everything you buy from the grocery or supermarket has the calorie content listed on the packet. Note that most manufacturers list calorie content by portion, and that even a lowly bar of chocolate usually has two portions. Marketing departments don't like the number of calories to be too high, as people won't buy it...so they'll just divide the product into more portions with a lower calorie count per portion. Sneaky!

Most foods have more calories than you might think. You can recognize the new practitioners of calorie restriction at the supermarket: they'll be the ones looking at many different product packages and muttering "wow, I had no idea!"

For foods like apples, rice, loose vegetables and so forth, you will need a book of calorie values. Recent editions tend to contain (fairly horrifying) values for fast foods as well as the more usual suspects. You might try the well regarded "Food Values of Portions Commonly Used":

• Food Values of Portions Commonly Used at Amazon.com

If you'd prefer an online reference, NutritionData provides a wealth of searchable information on various foods:

• NutritionData website

Remember the Supplements

You should always take a good multivitamin supplement (at the very least) when on a calorie restriction diet. In theory, it's perfectly possible to obtain all the vitamins and micronutrients you need from your food. In practice, for most people living busy, working lives, this just isn't going to happen. Remember to take your supplements.

The Water Trick

Doctors tell us that few people in Western societies drink as much water as they should for optimal health, and many people mistake low-level thirst for low-level hunger. A very helpful tactic for those practicing calorie restriction is to drink a glass of water when first feeling hungry. If you are still hungry twenty minutes later, then maybe it's time to think about eating. Half the time, you were just thirsty, however.

If You Have Questions, Ask!

There is a large and very helpful calorie restriction community out there.

• Where to Find Out More About Calorie Restriction
• Visit the CR Society website

Visit the CR blogs, take a look around, join the CR Society mailing lists and feel free to speak out. These folks have plenty of advice and helpful hints for newcomers. Everyone was new to calorie restriction at some point in the past, and there are no stupid questions.

It's Just a Diet, So Relax

Too many people approach diets in an all-or-nothing way. If they slip up or eat poorly one day, they become stressed or abandon the diet entirely in frustration. The key to health through diet is a relaxed attitude. If you slip up, let it go. Keep at it, do better next time, and stay working on the average.

Remember that a diet is simply a tool to make you healthier, and thus enable you to keep up with what you enjoy in life. Good luck in trying CR!

Addendum: The Future of Your Longevity

If you've read this far, you are probably interested in living a longer, healthier life. Calorie restriction is still the only widely available tool in the longevity toolkit today, which, when you stop to think about it, is a rather sorry state of affairs. This will not always be the case, however, as medical science and biotechnology are advancing ever onwards. It is worth remembering that, as time progresses, your remaining healthy life span is determined ever more by the rate of progress in longevity research - work aimed at repairing the accumulation of cellular damage, the roots of all age-related disease and infirmity. You should look into calorie restriction today, but also consider the long-term view: supporting medical research into extending healthy longevity is just as important ... and it will become ever more important as time goes on that you made that effort to help the development of better longevity medicine.

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Last updated October 24th, 2007