Is weight loss associated with increased risk of early mortality?

The current recommendations from major health organizations stipulate that if an individual has a BMI in the obese range (>30 kg/m2), they should be counseled to lose at least 5-10% of their body weight. This advice appears to make some sense given that increasing body weight is generally associated with heightened risk of various diseases, and that reduction of body weight usually improves levels of risk factors for disease (e.g blood pressure, triglycerides, etc). However, the literature has been much more complicated in terms of the effect of weight loss on risk of early mortality.

Adding to that literature is a study by Ingram and Mussolino published in The International Journal of Obesity. In essence this study showed that weight loss of 15% or more was associated with an increased risk of death from all causes among overweight men and among overweight and obese women.

In the study, a sample of 6117 adults above 50 years of age from the National Health and Nutrition Examination Survey (2888 men and 3229 women) were followed from 1988/94 to 2000.

Quite simply, the authors divided the sample into 3 categories of weight loss (<5%, 5-15%, and >15%) and evaluated the prospective risk of mortality depending on the degree of weight loss, with separate analyses in each gender and even within different BMI categories (normal weight, overweight, and obese).

While that may sound straightforward, the way they ascertained the degree of weight loss is quite a bit more convoluted. First they asked the subjects at baseline: ‘Up to the present time, what is the most you have ever weighed? (FEMALES): Do not include any times when you were pregnant.’

They then measured the participants’ body weight.

Finally, they calculated the subjects’ percent weight loss as:

((maximum weight – baseline weight)/maximum weight) x 100

During the follow-up time, there were 1602 deaths (835 men and 767 women). Interestingly, in contrast to persons with little or no weight loss (<5%, reference category), there was greater risk of early all-cause mortality among those who lost >15% of their maximum body weight, a finding which was statistically significant in overweight men, and in women of all weight categories (normal, overweight, and obese).

While these results may shock some of our readers, similar findings have been reported in numerous other studies. However, many such studies are confounded by various issues making the interpretation of their results rather difficult.

The major limitation to studies ascertaining the relationship between weight loss and mortality risk is delineating intentional (dieting, exercise, etc.) weight loss from unintentional weight loss (loss of body weight due to underlying disease, such as cancer). However, even studies that did separate between intentional and unintentional weight loss have shown conflicting results, suggesting that despite having positive effects on various indicators of health, weight loss may have a negative impact on longevity. Of course, even among those individuals who intentionally lose weight – the methods of doing so can vary widely, with some undertaking dangerous fad diets, extreme exercise or a regular regimen of random and often dangerous diet pills.

In this current study, all analyses were adjusted for age, race-ethnicity (white, black, Mexican-American), cigarette smoking status (current, former, and never), and history of health conditions related to excess weight and/or to weight loss. To try and control for unintentional weight loss, in addition to controlling for pre-existing health conditions statistically, respondents who died within 3 years of the baseline examination were also excluded.

Despite the new addition to the literature, the issue of weight loss and mortality is far from being sorted out. The concern is always that our ever increasingly obese population will see such findings as a reason to discontinue healthy lifestyle behaviors, or as a reason to maintain their currently poor lifestyle. It is key to remember that a healthy lifestyle has positive health effects regardless of what happens to one’s body weight.

Peter

Ingram, D., & Mussolino, M. (2010). Weight loss from maximum body weight and mortality: the Third National Health and Nutrition Examination Survey Linked Mortality File International Journal of Obesity, 34 (6), 1044-1050 DOI: 10.1038/ijo.2010.41

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10 Responses to Is weight loss associated with increased risk of early mortality?

  1. However, many such studies are confounded by various issues making the interpretation of their results rather difficult.

    Yes. And it also makes a difference how people lose weight. Forced caloric restriction has a different effect on the body than a low-carbohydrate diet with no caloric restriction, or a paleolithic diet that simply removes food toxins that contribute to inflammation and insulin resistance but does not restrict calories.

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    • Chris, you’ve posted previously about the touted benefits of a Paleo diet – suggesting that people can lose weight without a negative energy balance. As I previously responded, this notion is obviously flawed – I hope you can see that.

      I have also looked up the studies you had sent along, and they simply fail to support your assertion. First off, the paper published in Diabetologia did NOT show a difference in weight loss between the Medditeranean and Paleo diet (p = 0.3 for comparison of 0-12 wks – not significant). More important than that, is a fact which completely undermines the whole premise of both studies. In both cases, the individuals on the Paleo diet are consuming approximately 300-350 kcals less than those on the comparison diets (p < 0.01). I could care less what the results say, because this significant difference in energy consumption is a monstrous confounder. This is simply a comparison between a 1500kcal vs a 1800kcal diet. Not surprisingly, the one that cuts more calories to provide more benefit.

      Every few years comes along another fad diet proposing to be the answer to all man's ills – the paleo diet is simply another in a long succession. Of course there may be very good components to the diet itself – limiting sugar intake is a wonderful idea, for example – but it need not be a diet by some popular name. On the other hand, the strong focus on meat consumption as part of this particular diet may be less beneficial. Time and time again, evidence has shown that there is nothing magical about the composition of one's diet versus another in terms of weight loss – and yet, there is never a shortage of proponents for the effectiveness of THIS PARTICULAR DIET. All have their benefits, and drawbacks – eating sensibly (limiting saturated fat intake, salt, processed carbs, getting enough fibre, lean meats, etc.) should always be the goal regardless of the label (Atkins, Paleo, Medditeranean, etc).

      Travis and I started blogging as a way to provide evidence based information on issues that are often exploited by people trying to make a quick buck. There is plentiful misinformation in the world, and we've been trying our best to filter the BS from the truth for our readers. Thus, in the spirit of transparency and in the interest of our readers, I'd ask you to no longer leave comments supporting the Paleo diet on our site (future ones will be deleted).

      All the best.

      Peter

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  2. theshortearedowl says:

    The major limitation to studies ascertaining the relationship between weight loss and mortality risk is delineating intentional (dieting, exercise, etc.) weight loss from unintentional weight loss (loss of body weight due to underlying disease, such as cancer).

    I think it’s also the case that some (many?) people are always “intending” to lose weight, so if they lose weight due to unintentional reasons they may still attribute it to intentional weight loss. I would be interested to see if any papers attempt to control for this.

    …food toxins that contribute to inflammation and insulin resistance…</blockquote

    Whut?

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  3. Dr. Matthew says:

    As these types of designs grow in frequency, I find myself wondering about the impact of first having suffered harm before losing weight? For example, these aren’t simply overweight persons who then lost weight late in life, these are individuals, if I’m reading you correctly, who have already suffered negative health effects, and then late in life lose weight. Hearts, insulin systems, etc., are already affected. Are you aware of any longitudinal studies that look at changes in diet and exercise prior to permanent damage occurring? I can’t help but wonder if a person had lost the weight or changed lifestyle prior to that first heart attack, etc, if that would lead to a very different mortality profile.

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  5. Jennifer says:

    In your article, you refer to an “ever increasingly obese population.” The notion that we are getting fatter and fatter, and that we have an obesity crisis in the west is far from certain.

    In an NY Times article, Jeffrey Friedman argues that contrary to popular opinion, national (American) data do not show Americans growing uniformly fatter. Instead, he says, the statistics demonstrate clearly that while the very fat are getting fatter, thinner people have remained pretty much the same. We’ve put on a few pounds over the years, and this small gain has caused some people’s weight to go over that magical line between overweight to obese (using the BMI). This does not constitute a crisis, by any means. The only people who are seriously affected by weight gain are those who are at the extreme end of obesity.

    http://www.nytimes.com/2004/06/08/health/i-beg-to-differ-the-fat-epidemic-he-says-it-s-an-illusion.html?scp=1&sq=%22jeffrey%20friedman%22%20myth&st=cse

    I don’t see what is so hard to believe about weight loss being bad for longevity. We never evolved to lose weight. Our metabolism has many fail-safes built into it to prevent weight loss in order to ensure our survival. Given that Canadians are among the longest-lived people on the planet, perhaps we should worry less about scales and the BMI, and focus more on enjoying our long lives!

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  6. Nick says:

    This is really good info. Very interesting. I also found http://www.comparethediet.com which has some great stuff on diets and weight loss if your interested.

    Nick x

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  8. jim says:

    You are my inspiration, I have few web logs and occasionally run out from post :) .

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