Monday, June 27, 2005

Can Losing Weight Kill You?

In today's Guardian (UK) an article caught my attention - Overweight who diet risk dying earlier, says study. You can find the abstract on PubMed.

The first sentence of the article, Overweight people who diet to reach a healthier weight are more likely to die young than those who remain fat, according to a study, opens the door to a number of intriguing questions.
  • Did the researchers investigate enough factors to reach their conclusions, or is this merely a correlation and not causation?
  • Does the type of diet followed to lose weight influence the risk of losing weight?
  • How do we determine if/when the risk of losing weight outweighs the benefits?
What the researchers found was that in an 18-year follow-up of 2,957 overweight or obese people, data showed that those who wanted to lose weight and succeeded were significantly more likely to die young than those who stayed fat. Those who participated had been screened to ensure they had no underlying illnesses. Those who gained weight also had a greater risk of dying young.

So, the first of my questions, did the weight-loss cause more deaths or did something else increase the risk of early death?

That's a difficult question to answer since the researchers only looked at intention to lose weight, weight-loss, weight stability and weight-gain and did not investigate other issues related to health such as smoking habits, type of diet used for weight-loss, exercise habits, prescription and/or illicit drug use, or a host of other risks to long-term health.

"It seems as if the long-term effect of the weight loss is a general weakening of the body that leads to an increased risk of dying from several different causes," said Dr Sorensen. "The adverse effects of losing lean body mass may overrule the beneficial effects of losing fat mass when dieting," he added.

Ah, now there is something interesting - the loss of lean body mass as a factor that may increase risk! Which brings me to my second question - the type of diet used to lose weight. Again, the data is lacking here since the researchers didn't investigate the type of diets used to lose weight, so the nutritional quality of the diets used cannot be determined.

For years I've held the belief that the nutrient-density in the diet is of utmost importance when one is trying to lose weight. Dieting - that is creating a calorie deficiet to lose weight - is placing a strain on the body which has evolved with one primary function - survival. Choose a diet that is nutritionally bankrupt and the strain on the body is greater than when the body receives the nutrients it requires to function.

When one purposely creates a calorie deficit the potential for a nutrient deficit is higher. That is why it is critical to ensure you're body is meeting or exceeding nutrient requirements (vitamins, minerals, essential fatty acids, essential amino acids) while you are losing weight. These critical nutrients help the body "survive the famine" of calories.

The foods eaten (macronutrients - carbohydrate, fats, proteins) must be nutrient-dense. The evidence we have that has actually measured lean body mass loss compared to fat loss shows that a carbohydrate restricted approach with adequate protein intake is more protective to lean body mass than a fat restricted approach.

Which brings me to my last question - how do we determine if/when the risk of losing weight outweighs the benefit?

The authors stressed that very overweight people and those with weight-related illnesses should not be deterred from dieting, but added that researchers should in future consider the short-term advantages of weight loss against the potential long-term risks.

Losing lean body mass is potentially detrimental to overall health in the long-term. The key is to find a weight-loss diet that will help protect lean body mass and allow the body to shed fat stores. To date, the data supports a controlled-carbohydrate approach to lose weight while preserving more lean body mass when compared with other dietary approaches.

The caveat? Well, there a few...

Nutrient-density - if you choose a low-carb diet or a controlled-carb diet you must be vigilant about ensuring you eat nutrient-dense selections to meet or exceed the RDA's as you lose weight. Many find it helpful to track their eating in software that calculates nutrient intake along with calories, fats, carbohydrates and protein intake. Online there is a free service from that I highly recommend.

Calorie deficit - it is critically important that you do not send your body into a metabolic state of starvation while you're losing weight. If you restrict your calorie intake too much, your body can perceive the calorie deficit as "famine" and actually reduce your metabolism - slow down how quickly you use stored calories from fat and lean body mass - and be counter-productive to weight loss while also increasing the strain on the whole body to survive.

So how much of a deficit is too much?

A good rule of thumb is to ensure you're eating enough calories each day to meet your Basal Metabolic Rate (BMR) - that is how many calories your body requires just to function before any movement or activity is considered. The BMR is the calories required for body temperature regulation, blood flow, heart beat, breathing, etc. To find your BMR, you can use an online calculator that determines your BMR based on your current weight, height and gender. Be sure to re-calculate with each 10-pound loss since your BMR is closely tied to your current weight.

Activity - It's important to overall health that you're active. You don't need to go crazy, but you do need to get yourself moving. A good online calculator can help you determine how many calories you're using for a variety of activities - and it's based on how much you weigh and how many minutes you did the activity! If you're currently leading a "sedentary" lifestyle, start slowly and add more activity over time and as you lose weight.

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