Even though most researchers assert that a weight loss of 5% to 10% of body weight can lead to substantially beneficial health effects, most patients set expectations for themselves of far more ambitious weight loss goals, regardless of the method they use to lose weight. For example, Heinberg et al, in a 2010 article in Obesity Surgery, report that patients undergoing bariatric surgery (the most dramatic way to lose weight) will lose, depending on the surgical procedure used, up to 80% of their excess body weight, but many of
these patients will lose considerably less and may have unrealistic expectations to lose close to 100% of their pre-surgical excess body weight! These researchers even caution that surgical informed consents should make explicit to patients the amount of weight loss actually expected from surgery. Typical weight loss for the gastric lap band surgery (recently undergone by Governor Chris Christie of New Jersey), for example, is only about 20 to 25% of general body weight, according to Sjöström et al (The New England Journal of Medicine, 2007) Results from lifestyle changes (e.g. diet and exercise) and even psychopharmacological treatment generally yield far lower percentages.
Dieters can be somewhat persistent and not so malleable in their wish to change their expectations. For example, Wadden et al, in a 2003 article cleverly called Great Expectations: ‘I’m losing 25% of my weight no matter what you say’ (and the inspiration, other than Charles Dickens, for this blog’s title) found that even when patients are “informed repeatedly” that their weight loss goals were unrealistic, they still expected to lose twice as much as they had been advised. These researchers found that some obese patients, though, may actually “be surprised to find they are generally satisfied by the 10% weight loss now recommended by health professionals.”
So does it matter whether you set so-called “realistic goals” for weight loss? This has become common parlance among many clinicians who discuss weight control with their overweight and obese patients. After all, so the argument goes, setting goals that are too ambitious may lead dieters to give up and experience considerable disappointment and a sense of failure. Apparently, though, there is no scientific evidence (i.e., “no statistically significant relationship”) to support this widely held belief and it is actually one of several weight loss myths uncovered by David B. Allison, Ph.D., Quetelet Endowed Professor of Public Health, and his group at the University of Alabama at Birmingham.
For this particular myth, Dr. Allison et al did a thorough search of the literature from 1998 to 2012 and conducted the first meta-analysis of randomized controlled studies (11 met their inclusion criteria) that investigated the relationship between goals set by patients for weight loss and their actual weight loss. Publishing this year in the journal Obesity Reviews, they found “current evidence does not demonstrate that setting realistic goals leads to more favourable weight loss outcomes,” apparently regardless of the weight loss intervention (e.g. cognitive behavioral therapy, dietary modification, use of medication or even bariatric surgery.) Even when patients’ goals became more realistic, they did not necessarily lose more weight or even have better psychological outcomes as measured by less evidence of depression or greater self-esteem. The researchers found, though, that there was not a consistency among studies in the terminology used in their description of “weight loss goals.” For example, some studies assessed “maximum acceptable weight loss goals” while others assessed “dream/ideal weight loss goals.” One limitation of their meta-analysis, they note, is that they focused on goals for the “active phase” of weight loss rather than on goals during the important phase of maintenance of the weight lost, and they acknowledge that these phases (and the behaviors involved) may be quite different. The researchers conclude, “While the assertion that unrealistic goals lead to disappointment and discontinuation of weight loss efforts makes intuitive sense, the empirical evidence does not support this conclusion.”
What may be more important in achieving ambitious weight loss goals, for example, may be an individual dieter’s motivation, autonomy (“ownership over newly adopted behavioral patterns”) and self-determination, i.e., “a sense of choice and volition,” rather than feeling pressure to comply or feeling controlled, according to Teixeira et al (International Journal of Behavioral Nutrition and
Physical Activity, 2012). These researchers even question the standard “continuous care” model for treating excess weight in that they believe it may interfere with some dieters’ own sense of self-efficacy. For Teixeira et al, general self-efficacy (i.e. an “overall sense of assurance or self-confidence”) may be more predictive of successful weight loss than self-efficacy for specific behaviors (e.g. eating) or even goals patients set.
For a discussion of other weight control myths found by Dr. Allison and his group, please refer to their article, Myths, Presumptions, and Facts about Obesity, published this past year in the January 31st issue of The New England Journal of Medicine, as well as refer to one of my previous blogs, The Hare and the Tortoise: Aesop’s Fable and Weight Loss (https://cdn.psychologytoday.com/blog/the-gravity-weight/201303/the-hare-...) on another of their myths concerning the spurious relationship of rapid weight loss leading necessarily to weight regain.