Welcome to part nine of The science behind weight loss, a Conversation series in which we separate the myths about dieting from the realities of exercise and nutrition. Here, Lennert Veerman, Senior Research Fellow at the University of Queensland’s School of Population Health, assesses the cost effectiveness of prescription weight-loss medicines:
If you have a problem with your health and visit a general practitioner, you might be prescribed medication to alleviate symptoms and make you feel better.
But what if your health concern is excess weight?
Pharmacology is just one of several options to treat obesity, along with lifestyle changes and the more radical option, bariatric surgery.
So how effective are weight-loss drugs? And are they worth the cost?
Last week, we published a study on the cost effectiveness of weight-loss drugs in the international science journal PLOS One. It was part of our NHMRC-funded ACE Prevention study, which examined the cost effectiveness of 150 public health interventions in Australia.
An earlier 2008 systematic review found most published studies reported anti-obesity medications were cost effective. So we were initially optimistic our review would uncover similar findings.
Prescription weight loss medications
The most commonly prescribed drugs to aid weight loss are sibutramine and orlistat.
Sibutramine (also known under trade name Reductil) belongs to a class of drugs called norepinephrine and serotonin reuptake inhibitors, which are usually prescribed to treat depression. Sibutramine is thought to aid weight loss by suppressing the appetite and increasing metabolism.
Orlistat (Xenical) is a lipase inhibitor which appears to aid weight loss by preventing the digestion and absorption of dietary fat.
Both were available in Australia and subsidised under the Pharmaceutical Benefits Schedule (PBS) until late last year, when sibutramine was withdrawn due to safety concerns.
Effectiveness
In our study, we assumed obese patients would take orlistat or sibutramine as directed, for a period of 12 months. But trials have shown that about half the participants using sibutramine and one third of orlistat users had stopped before the end of the year.
This may have been because they experienced some common side effects, such as increased blood pressure for sibutramine and abdominal complaints for orlistat.
On average, people who started taking sibutramine lost 4.5 kg from the drug alone. For orlistat the average weight loss was 2.9 kg. But this wasn’t sustained.
The little available evidence shows that once people stopped taking the drugs, they quickly regained the weight they had lost. After about a year, they were likely to be at their original weight.
(Interestingly, the weight lost through diet and exercise interventions also came back but around four times slower, as participants gradually reverted to their old habits.)
Cost-effectiveness
One year of treatment with either drug costs around $1,475. Quite an expense for just a few kilograms of weight loss over a short period of time.
But in assessing the cost effectiveness of a medicine, we need consider how the benefits of person’s weight loss will reduce the cost of their health care later in life.
On average, every “healthy life year” gained with sibutramine cost about $140,000. This means a large number of people need to be treated with the drug before it adds up to gains that equal one year of good health. Orlistat allows “buying” healthy life years at a net price of around $240,000 each.
Health interventions that cost less than $50,000 are usually considered good value for money. Statin drugs, which lower cholesterol, for instance, cost around $25,000 per healthy life year and diuretics (used to reduce blood pressure) cost around $2,000 per healthy life year.
Using this cost-effectiveness threshold, neither obesity drug seems to be a very good buy. Further, they only reduce the rates of obesity-related disease – such as type 2 diabetes, heart disease and osteoarthritis – by a small percentage.
Different conclusions
Our results aren’t in line with most previous studies, which concluded both drugs offer good value for money.
Several factors may have contributed to this discrepancy, including incorrect assumptions that:
Everybody would continue taking their medication.
The weight would come back over three or five years (not one year, as the evidence shows)
23% of the weight reduction was permanent (for which we found no evidence).
Another consideration is that 11 out of the previous 14 studies were paid for by the pharmaceutical company that marketed the particular drug.
The few independently funded studies found much less favourable results, with an average of €62,000 (A$82,000) per healthy life year for independent studies, compared with €15,000 (A$20,000) for industry-sponsored studies.
Cost-effectiveness analysis is a process in which many decisions add up to rather opaque models. You can achieve almost any result you want by tweaking the assumptions. So studies funded by parties with vested interests ought to be treated with caution.
It’s important to note that side-effects of drugs may only become evident after some time. Sibutramine is a case in point: it was taken off the market last year because trials showed it increased the risk of heart attack and stroke.
So it’s clear that current obesity drugs aren’t the silver bullets that will halt or reverse the obesity epidemic.
Well-designed diet and exercise interventions are less expensive and more effective than current pharmacotherapy. But the best bet for lasting weight loss is to change our “obesogenic” environment, through limiting the availability and advertising of unhealthy foods.
This is the ninth part of our series The science behind weight loss. To read the other instalments, follow the links below:
Part One: Diets and weight loss: separating facts from fiction
Part Two: Want to set up a weight loss scam? Here’s how…
Part Three: Feel manipulated? Anxious? Tune out the hype and learn to love your body
Part Four: Food v exercise: What makes the biggest difference in weight loss?
Part Five: An online tool to help achieve your weight-loss goal (no, it’s not a fad diet)
Part Six: Ignore the hype, real women don’t ‘bounce back’ to their pre-pregnant shape
Part Seven: Quick and easy, or painful and risky? The truth about liposuction
Part Eight: Weight loss and the brain: why it’s difficult to control our expanding waist lines
Part Ten: Want to try the latest fad diet? Just ask your local pharmacist
Join the conversation
Comments (10)
Guy Hibbins
(Clinical evaluator of therapeutic goods at Monash University)
While the psychoactive weight loss drugs may be effective in the short term they share the same problems as other psychoactive drugs; namely tolerance, dependence, withdrawal symptoms and the central nervous side effects of stimulants in general such as insomnia.
A good review of this is to be found in Heit J "Is there a Magic Pill for Weight Loss?" HealthCentral June 12 2008 http://www.healthcentral.com/obesity/c/45116/30705/magic-pill-weight
In relation to fat absorption inhibition, any drug…
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Colin MacGillivray
Retired architect (logged in via email @gmail.com)
Wow mangosteens for dieting. Excellent
For those who have never seen one:
http://en.wikipedia.org/wiki/Mangosteen
Possibly the most delicious fruit ever but they deteriorate badly once off the tree (the ones in our garden do anyway).
Here's a great diet:
Weigh yourself every week and if you've gone up a kilo from last week eat less food till the next week.
Doug Cotton
(IT Manager)
Yes, Colin and Guy. Actually I weigh myself daily and can just about guess within 0.2Kg what I will weigh based on fat consumption the previous day. I have certainly observed a correlation between cholesterol and weight also.
If you are interested in the weight loss effect of mangosteens, just google it and "weight" and you'll see links like http://www.mangosteenfacts.org/mangosteen-weight-loss.html
Personally I'll stick with the extract in capsule form for year-round use. Will let you know in a few weeks how it's going as I'd still like to drop from 78 to 73Kg for a BMI around 22..
Doug Cotton
(IT Manager)
In anticipation of questions, here's some more detail on the above plant extracts in the new "diet pill" ....
"In a key human clinical study(1) using a proprietary blend of East Indian globe thistle and mangosteen rind extracts, 60 obese subjects with Body Mass Index (BMI) of 30-40 were included in a randomized, double-blind, placebo-controlled study for eight weeks. Participants followed a 2,000 calorie-a-day diet and asked to walk 30 minutes five days a week. The experimental group was given…
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Scott Waye
Academic Health Advisor (logged in via email @yahoo.com)
Sadly this article does not address the issues of abuses and obesity; you have omitted the weighty matter of emotional abuses and clinical depression http://foodaddictions.wordpress.com/2011/11/14/depressiondepressed-and-eating-too-much/ that are prevalent in western societies. We cannot ignore this most prevalence effect that leads to overeating which are abuses. This is a stark error. Psychiatrist David Dunkley of JGH
“Childhood sexual abuse or emotional abuse were associated with greater body dissatisfaction in [binge eating disorder patients], whereas physical abuse or physical or emotional neglect were not,” said David Dunkley, a psychiatric researcher and clinical psychologist at Jewish General Hospital. The blaming of advertising and McDonalds is a very narrow minded view as is the use of medications that do not address the underlying causes.
Lennert Veerman
(Senior Research Fellow, School of Population Health at University of Queensland)
Well, this particular article is about pharmacological therapy to lose weight, not about the causes of obesity.
But I grant you that advertising and junk food aren't the only factors that drive overeating. But to assume that emotional abuse and clinical depression are the cause of the enormous increase in average body mass that we have seen over the past decades, you would have to assume that they have increased a lot as well. I don't think there is much evidence for that. And if there were, I would…
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Doug Cotton
(IT Manager)
From my experience one can gain reasonable benefits from just one orlistat capsule per day taken with the evening meal, if other meals can be restricted in fat intake and snacks avoided. This keeps the cost down to about $10 a week.
The timing of meals and exercise is also important, there being benefits in exercising after a 12 to 14 hour fast when the body is forced to burn fat. Hence, an early evening meal, then exercise before a late breakfast may be possible, at least on days when one is not working.
However, I am looking forward to testing two plant extracts in a supplement I expect to receive soon from the US, namely extracts from Sphaeranthus indicus (S. indicus) and the mangosteen fruit (Garcinia mangostana.) At least these will be somewhat cheaper than orlistat and perhaps also beneficial in other respects.
Lennert Veerman
(Senior Research Fellow, School of Population Health at University of Queensland)
Ha Doug, I expected you.
"From my experience..." counts as anecdotal evidence, which occupies the lowest rank in the hierarchy of evidence.
That said, one could argue that it is very contextually relevant in your case. And with the fat restrictions in other meals, the avoidance of snacks and exercise before breakfast I'm sure the package is very beneficial. (Though you might consider excepting polyunsaturated fat from your restrictions.)
Andrew Pengilley
Doctor (logged in via email @gmail.com)
What is most revealing about trials of diet medications is that the placebo response is fairly high. This is because, at least all the ones I've seen, have been trialed with a calorie restricted diet. And suprise, actual compliance with a calorie restricted diet in the context of a clinical trial works.
This is basic thermodynamics and, as with the perpetual motion machine, there is no such thing as a free lunch. If you don't absorb the calories they remain in the gut - see Orlistat. If you do…
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Scott Waye
Academic Health Advisor (logged in via email @yahoo.com)
Diet pills are medications and this is not the best road to take to reverse obesity. The USA,England and Australia use dangerous food chemicals that can create Diabetes and Obesity. Food chemicals like high fructose corn syrup( it is really a chemical not natural)is a danger and should be outlawed
4 million died from Diabetes and obesity this year. http://spirithappy.org/wp/2011/09/14/diabetes-now-kills-4-6-million-every-year-diabetic-overweight-or-thin-the-illness-is-taking-lives/
Princeton University found that high fructose corn syrup was a cause of obesity.
"Some people have claimed that high-fructose corn syrup is no different than other sweeteners when it comes to weight gain and obesity, but our results make it clear that this just isn't true, at least under the conditions of our tests," said professor Bart Hoebel who specializes in the neuroscience of appetite, weight and sugar addiction.