Most people think a low-calorie diet is the epitome of health. Diet drinks stress their lack of calories as a major selling point, as do perfectly portioned meals. “Eat small amounts, as few fats as possible, and you’ll feel better” – or so the advice goes. But how healthy is a restricted calorie diet? Should we all just be eating less?
When low-cal is good: when you already take in more calories than you burn
When you restrict your calorie intake, you restrict the food available to be turned into fats. This is clearly good if you’re already obese. I could cite a hundred studies that discuss the health detriments of excess fat on our bodies, but I know you’ve heard them all before. Being obese is dangerous to just about every organ in your body.
Moreover, it makes exercise more difficult and, therefore, it is much more difficult to stay healthy. Cutting calories is an easy way to help yourself lose weight. One study in mice, genetically altered to become obese on a normal diet, found that a calorie restricted diet lengthened their lifespan and kept down their weight1.
Similar results have been found in people who are overweight and obese. Cutting calories has been found to lower cardiovascular risk factors and help people lose weight. Success stories are often told about getting fit and healthy on a low-calorie plan – that’s how it has become so popular. Most weight loss clinics and pay-per-meal systems utilize cutting calories as a major portion of the program; just think about weight watchers ‘points’ per food item. So, if you overeat or are overweight, cutting down might be a good idea.
When low-cal isn’t good: when you’re already healthy
Yes, cutting calories helps you lose weight and keep your body from forming fat reserves. But that’s only important if you have excess weight to lose and fat reserves to spare. Otherwise, you’re starving your body of nutrients and fuel. That same study which found lifespan extensions for obese mice on a low-cal diet found that restricting calories from normal mice actually decreased their lifespan1.
People with normal metabolisms might do more harm than good by cutting calories. Even those that are overweight and obese should be careful. Dropping pounds too quickly isn’t healthy, no matter how much you have to lose. Dropping pounds too quickly raises toxins in your system which can lead to a variety of problems as well as putting the weight back on.
Cutting calories can have other detrimental effects, especially in normal or underweight people2. It’s been shown to lower immune function, even when only done in a short-term manner 3. It’s like the old adage says – you have to “drown a cold and feed the flu.” By taking away calories, you also take away the fuel your body needs to boost your immune system when you’re sick.
Studies have found that mice are more susceptible to the flu virus and its ill-effects on low calorie diets even when they got the same dose of vitamins and minerals that are in a normal diet4 – so you can’t just chew on some Flintstones or pop a One-A-Day to make up for the food you aren’t eating.
Also, your idea of “overweight” or “fat” might not even be unhealthy. Studies have found that being too thin is just as dangerous as being too fat, and a little extra padding, especially around the thighs and butt, might actually lower your risk of diabetes and other diseases5. The fat around those areas is different from abdominal fat, and helps the body make better use of its insulin to break down sugars.
So what’s the verdict?
Unless you’re really overweight, you’re probably better off just eating nutritiously, not cutting down calories. Some foods with high calories are very good for you – like olive oil and certain other oils, for example. Eat better, not less.
If you are considering a low-cal diet, be sure to keep up your intake of vitamins and minerals – losing nutrition isn’t going to help you in the long run. Instead of trying to eat smaller portions, try exercising more and eating power foods like blueberries. And, as with anything, talking to your doctor before making drastic changes is always a good idea. A low-cal diet is just like taking medicine – you only want to do it when you have to, and it’s not for everyone!
1. R. S. Sohal, M. Ferguson, B. H. Sohal, M. J. Forster (2009). Life Span Extension in Mice by Food Restriction Depends on an Energy Imbalance Journal of Nutrition, 139 (3), 533-539 DOI: 10.3945/jn.108.100313
2. Amie J. Dirks, Christiaan Leeuwenburgh (2006). Caloric restriction in humans: Potential pitfalls and health concerns. Mechanisms of Aging and Development, 127 (1), 1-7 DOI: 10.1016/j.mad.2005.09.001
3. Christopher A. Jolly (2007). Is dietary restriction beneficial for human health, such as for immune function? Current Opinion in Lipidology, 18 (1), 53-57 DOI: 17218833
4. B. W. Ritz, I. Aktan, S. Nogusa, E. M. Gardner (2008). Energy Restriction Impairs Natural Killer Cell Function and Increases the Severity of Influenza Infection in Young Adult Male C57BL/6 Mice. Journal of Nutrition, 138 (11), 2269-2275 DOI: 10.3945/jn.108.093633
5. T TRAN, Y YAMAMOTO, S GESTA, C KAHN (2008). Beneficial Effects of Subcutaneous Fat Transplantation on Metabolism. Cell Metabolism, 7 (5), 410-420 DOI: 10.1016/j.cmet.2008.04.004