Teen Skepchick Interviews: Diana Williams
This post is part of the Teen Skepchick Interviews series, where TS writers talk with amazing women scientists and skeptics about life, the universe, and everything.
If any of you are like me, you have your share of friends and family members who are semi-pro dieters, the ones who seem to have an implanted heads-up display that tells them portion sizes and calorie content every time they look at food; those who try every fad diet on the market, from eating only cabbage soup to injecting themselves with the HCG hormone. You probably also know people who have the opposite problem. No matter how much they eat, how much weight-gain powder they choke down, they can’t seem to gain weight.
I’ve tried my share of diets, and like other family members, I’ve struggled with my weight, even when I’ve approached dieting sensibly, by changing bad habits without actually “dieting.” So I decided it was time to ask an expert. Do any diets work? Diana Williams, who researches neuroendocrine control of food intake, body weight, and metabolism, answered this question and more based on what the science actually says. The answers are both depressing and liberating.
Do any diets actually work?
It depends on what you mean by “work.” Without a doubt, it is possible for many people to lose weight by restricting their food intake, but that weight loss does not last in the long run for most people, who regain most or all of the lost weight within a few years, with some people ending up heavier than they were when they started the original diet. Many studies have examined maintenance of weight loss, and the general finding is that regardless of the specific diet people used, about 30% of that lost weight is regained within 1 year, with the rest regained 2-5 years later. On average, when you look at their weight 5 years after the original weight loss occurred, folks are only 3.2% lighter than they were before they started the diet.
Does it work better to make lifestyle changes instead of dieting?
Lifestyle changes are really just another kind of diet. People like to use that term to differentiate somewhat more reasonable approaches (often intended to be lifelong) from more extreme or just plain wacky diets, but they work no better in the long run. This is also true of high-protein, low-carbohydrate diets. Some studies have found greater initial weight loss with low-carb diets, but not only is most of that weight regained, a recent study reported that people who lost weight on low-carb diets actually experienced more regain over 3 years than those who had lost weight on low-fat diets.
Why do people regain the weight? Is it psychological? Biological?
This regain of lost weight is not due to laziness or lack of willpower. It happens because we have a strong and complex biological system that functions to keep whatever fat we have—even if you feel that you’ve got too much, your body does not want to let it go. This system responds to weight loss in a heavier person exactly the same way as it does in a thin person. Through coordinated responses of many hormones and brain circuits, two major things happen: (1) the person losing weight will be hungry and less satisfied by smaller amounts of food; and (2) this person’s body will change the way it uses energy in order to burn less and conserve more. While it may be possible to fight against the powerful drive to eat, no amount of self-discipline will prevent these metabolic changes from occurring. Physical activity actually burns fewer calories in weight-reduced people. A weight-reduced person is not physiologically the same as a person who’s been at that same lower weight all along.
For example, one of the major players in this compensatory response to weight loss is the hormone leptin, made by fat cells. Leptin sends signals to the brain about how much energy you have stored in your body in the form of fat. Normally, leptin is produced in direct proportion to fat mass—you have more fat, you have more leptin. But when you lose weight and lose fat, leptin levels drop precipitously, off that proportional curve. So a person who’s lost 40 lbs to wind up at 150 lbs has a lower leptin level than a person who was 150 lbs all along. This drop in leptin levels sends an “emergency” signal to the brain that we may be in a starvation situation, and that causes a reduction in energy expenditure to conserve the fat that we have left, plus produces a powerful drive to find and eat more food. This is just one of many physiologic responses that coordinate to prevent, limit, and reverse weight loss.
But some people do lose weight and keep it off, right? Why are they different?
The National Weight Control Registry tracks volunteers who have lost 30 or more pounds and kept it off for 1 or more years. They’ve reported that these folks eat a low-calorie low-fat diet, and many limit the variety of foods in their diet and eliminate some foods altogether (e.g., French fries, cheese). They also exercise for about 1 hour per day. Given their physical activity level, they eat about 700 kcal/day fewer than someone who had never lost weight would require. Yet they are not losing weight, just maintaining. So this really tells us that these people are still working against those biological changes that I mentioned earlier, even years after the initial weight loss.
This was recently confirmed in a study of people who had lost weight in a 10-week program. One year later, they had gained about 40% of the weight back, but their hormones were still in the same state that they were immediately after that 10-week program. So even 1 year later, they felt hungry and preoccupied with food because the hormones that control hunger and fullness were sending their brains the message that they needed to eat more and regain that lost weight. When you understand the biological response to weight loss, it’s easy to see why diets don’t work in the long run. You’re up against a powerful biological system that you really cannot control.
So if we all have these biological reactions, why are some people thinner than others?
It may come as a surprise to some, but thin or fat, we don’t have that much control over our body weight. It is heavily influenced by our genes, with an estimated heritability of 60-90% depending on the study. Several of the specific genes involved have already been identified, though there are surely many more to be found. Although our environment, eating habits, and physical activity levels can affect weight, these factors only account for relatively small differences. Researchers in this area often talk about a set range or settling point for body weight. There’s a lot of debate about the details, but the basic idea is that our bodies “defend” a relatively narrow range of weight, sometimes estimated to be around 10-15 lbs.
It works both ways: not only do our bodies defend against weight loss, evidence suggests they defend against weight gain out of that range. This was clearly shown in a classic experiment now known as the Vermont Prison Study, published by Ethan Sims in 1968. He had healthy, thin men volunteer to overeat in an attempt to cause obesity. Some of these guys were eating 8000-10,000 kcal each day (that’s 4-5 times normal), but it was very difficult for them to gain weight. Only some gained 20-25% of their initial body weight, while others gained almost nothing despite eating so much. Their metabolic rates increased to burn off the excess energy they consumed. When the overfeeding regimen was finished and they could go back to eating whatever they wanted, those who had gained weight quickly lost it with no special effort and went back to their original lean body weight. This is a dramatic demonstration that overeating and sedentary behavior don’t make genetically thin people fat, and it’s another indication that obesity is not the result of laziness and gluttony.
Are you just saying these things because you’re part of the conspiracy of scientists to rule the world and make everyone fat?
No way, I’m not interested in ruling the world! And as I discussed earlier, I couldn’t make a genetically thin person fat if I tried. Seriously though, consider who benefits from the myth that we can all be any size we want if we follow the right plan or buy the right product. There is a huge diet and weight loss industry making money off people who desperately want to be thin. I’d like to see people focus less on what they weigh and more on actual health and fitness.
This interview will be continued next week, when Dr. Williams will tell us more about diet, weight, and health from a scientific, skeptical perspective, including whether we should start building our underground shelters to protect us from the OMG OBESITY EPIDEMIC!! See part 2 here.
Disclaimer: No statements made in this interview should be taken as medical advice.
Dr. Diana Williams received her PhD from the University of Pennsylvania Department of Psychology in 2003, and trained as a postdoctoral fellow at the University of Washington School of Medicine, Department of Medicine, Division of Metabolism, Endocrinology and Nutrition, from 2003 to 2008. In 2008, she joined the faculty of Florida State University as an assistant professor in the Department of Psychology and Program in Neuroscience. Her laboratory focuses on the neural and endocrine control of food intake and body weight.
Resources and References
Gina Kolata’s Rethinking Thin, 2007, Picador
David Kessler’s The End of Overeating, 2009, Rodale Books
Blogs & web sources:
- Science Watch interview with Katherine Flegal about her research on prevalence of obesity and obesity-associated mortality: http://www.sciencewatch.com/ana/st/obesity2/10sepObes2Fleg/
- Obesity Panacea: http://blogs.plos.org/obesitypanacea/
- Dr. Sharma’s Obesity Notes: http://www.drsharma.ca/
- Weighty Matters: http://www.weightymatters.ca/
- National Weight Control Registry: http://www.nwcr.ws/
- Dr. Stephen Barrett’s Quackwatch Diet Scam page, not updated frequently but a good source for information on many scams that are still going strong: http://www.dietscam.org/
Maintenance of weight loss:
Anderson JW, Konz EC, Frederich RC, Wood CL. Long-term weight-loss maintenance: a meta-analysis of US studies. Am J Clin Nutr. 2001 Nov;74(5):579-84.
Anderson JW, Vichitbandra S, Qian W, Kryscio RJ. Long-term weight maintenance after an intensive weight-loss program. J Am Coll Nutr. 1999 Dec;18(6):620-7.
Lowe MR, Kral TV, Miller-Kovach K. Weight-loss maintenance 1, 2 and 5 years after successful completion of a weight-loss programme. Br J Nutr. 2008 Apr;99(4):925-30.
Lowe MR, Miller-Kovach K, Phelan S. Weight-loss maintenance in overweight individuals one to five years following successful completion of a commercial weight loss program. Int J Obes Relat Metab Disord. 2001 Mar;25(3):325-31.
Tsai AG, Wadden TA. Systematic review: an evaluation of major commercial weight loss programs in the United States. Ann Intern Med. 2005 Jan 4;142(1):56-66. Review.
Comparison of low-carbohydrate diets:
Foreyt JP, Salas-Salvado J, Caballero B, Bulló M, Gifford KD, Bautista I, Serra-Majem L. Weight-reducing diets: are there any differences? Nutr Rev. 2009 May;67 Suppl 1:S99-101. Review.
Foster GD, Wyatt HR, Hill JO, Makris AP, Rosenbaum DL, Brill C, Stein RI, Mohammed BS, Miller B, Rader DJ, Zemel B, Wadden TA, Tenhave T, Newcomb CW, Klein S. Weight and metabolic outcomes after 2 years on a low-carbohydrate versus low-fat diet: a randomized trial. Ann Intern Med. 2010 Aug 3;153(3):147-57.
Fung TT, van Dam RM, Hankinson SE, Stampfer M, Willett WC, Hu FB. Low-carbohydrate diets and all-cause and cause-specific mortality: two cohort studies. Ann Intern Med. 2010 Sep 7;153(5):289-98.
Biological response to weight loss:
Maclean PS, Bergouignan A, Cornier MA, Jackman MR. Biology’s response to dieting: the impetus for weight regain. Am J Physiol Regul Integr Comp Physiol. 2011 Sep;301(3):R581-600.
Rosenbaum M, Hirsch J, Gallagher DA, Leibel RL. Long-term persistence of adaptive thermogenesis in subjects who have maintained a reduced body weight. Am J Clin Nutr. 2008 Oct;88(4):906-12. PubMed PMID: 18842775.
Rosenbaum M, Vandenborne K, Goldsmith R, Simoneau JA, Heymsfield S, Joanisse DR, Hirsch J, Murphy E, Matthews D, Segal KR, Leibel RL. Effects of experimental weight perturbation on skeletal muscle work efficiency in human subjects. Am J Physiol Regul Integr Comp Physiol. 2003 Jul;285(1):R183-92.
Sumithran P, Prendergast LA, Delbridge E, Purcell K, Shulkes A, Kriketos A, Proietto J. Long-term persistence of hormonal adaptations to weight loss. N Engl J Med. 2011 Oct 27; 365(17):1597-604.