Julia Belloz at Vox – We’ve long blamed carbs for making us fat. What if that’s wrong?
The main scientific model behind the low-carb approach is the “carbohydrate-insulin hypothesis,” which journalist Gary Taubes, Harvard professor David Ludwig, and others have extensively promoted. It suggests that a diet heavy in carbohydrates (especially refined grains and sugars) leads to weight gain because of a specific mechanism: Carbs drive up insulin in the body, causing the body to hold on to fat and suppress calorie burn.
But what’s often lost in all the boosterism around the low-carb approach is that it is still an unproven hypothesis in science.
So they did a study to show whether a low-carb diet can actually help to reduce weight. 17 overweight or obese men in a metabolic chamber for 4 weeks and fed either a high carbohydrate diet or ketogenic diet with the same number of calories. Results? No increased body fat loss with the ketogenic diet.
But as Bazinet points out, “The study … doesn’t see any [relationship between a decrease in insulin and an increase in fat loss]. Show me a better study that supports this.”
There isn’t any, he added.
Tobias urged dieters not to lose sight of the bigger picture. “Low-carb versus low-fat should not be the focus for people selecting a weight loss diet.” The focus, she said, should be on improving the quality of food that people eat instead.
Jill Eisen for the CBC – Fat and Sugar, Part 1
First, fat was the dietary bad guy. We were warned back in the 1980s to cut back on eggs, meat and full-fat dairy to avoid heart disease. So we started eating more bread, rice and pasta and fat-free snacks. But we got sicker and fatter. Now sugar is the bad guy. Contributor Jill Eisen explores the complex, and sometimes contradictory, science of nutrition — and tries to find clarity amidst the thicket of studies and ambiguous research.
There’s also a great list of research references and a reading list at the link, for more information.
Part 2 airs on June 22, 2016.
A doctor and a professor discuss – Are there health benefits to being overweight?
Carl J. Lavie:
The good news for those who may be struggling to lose weight and keep it off is this: As I explored in my book “The Obesity Paradox,” there can be surprising benefits to carrying around a few extra pounds. In fact, being out of physical shape and having low overall fitness is actually a far greater danger to health than fat, especially in people who are only slightly overweight.
Using information on weight history, it is possible to address this seemingly intractable source of bias. Weight history makes it possible to distinguish people who were slim throughout their lives from those who were formerly overweight or obese but lost weight.
In other words, Stokes is claiming that most studies include weight at the start of the study and throughout the study, but neglect the weight history of the person. The formerly overweight/obese who were ‘normal’ weight at the time of the study may have higher mortality due to issues related to the former excess weight, and therefore skew the results to look like overweight people have lower mortality (as a group). Interesting.
The study by Stokes and Preston goes into further depth on the weight history theory. The conclusions are stark (emphasis mine) :
Our results suggest the burden of overweight and obesity on mortality is likely substantially larger than commonly appreciated. If correct, this may have serious implications for the future of life expectancy in the United States. Although the prevalence of obesity may level off or even decline, the history of rapidly rising obesity in the last 3 decades cannot be readily erased (63). Successive birth cohorts embody heavier and heavier obesity histories, regardless of current levels. Those histories are likely to exert upward pressure on US mortality levels for many years to come.
Shirley Cramer, chief executive of the Royal Society for Public Health – Food should be labelled with the exercise needed to expend its calories:
The Royal Society for Public Health has called for the introduction of “activity equivalent” calorie labelling, with symbols showing how many minutes of several different physical activities are equivalent in the calories expended to those in the product. The aim is to prompt people to be more mindful of the energy they consume and how these calories relate to activities in their everyday lives, to encourage them to be more physically active.
As reported by the CBC, not everyone is a fan of this approach:
Not everybody is sold on the idea. Dr. Yoni Freedhoff is the medical director of the Bariatric Medical Institute in Ottawa.
“People believe that exercise is the ticket to the weight loss express,” he said.
But, in fact, exercise doesn’t burn that many calories.
I believe Dr. Freedhoff is correct. Labelling foods with exercise equivalents is not the right message, and mixes up the idea of weight loss with exercise, when they are not well linked at all.
From what I’ve been reading, exercise is key for reducing your risk of dying early due to cadriovascular disease. With better fitness you also reduce your risk of physical injuries. However, the amount of exercise you do is not well correlated to your weight. Meaning that you cannot realistically exercise enough to reduce your weight if you are consuming the same amount of calories.
– More exercise => better fitness and live longer
– Fewer calories => lose weight
See Dr. Freedhoff’s talk on the issue:
David Katz on America’s Test Kitchen Radio episode 405 (interview starts at time stamp 17:20).
On calories in vs calories out (22:30):
You get differential disposition of calories depending on what they are from and how that affects physiology.
So for example, calories from sugar will evoke an insulin response, and insulin in turn increases the tendency that calories will be deposited not only in body fat, but body fat in a harmful place right around the middle. If you get your calories from monounsaturated oil or omega3 oil or high quality protein you’re going to have a different insulin response and those calories will go to different places in your body. So yes, the nature of the calories matters.
The other critical thing here, Chris, and the thing I was about to say this is, the quality of foods that we eat profoundly influences the number of calories it takes to feel full.
On science vs hucksters (30:18):
You maintain, Chris, that the public knows what to do, and that’s a huge part of the problem. See, somebody like me, I really want to empower people with useful information but you ask me any question and I start hemming and hawing, right? There’s subtlety, there’s nuance, but you talk to the hucksters and the charlatans or the fools and fanatics, and they’ll tell you, “Geez you know, Katz is dull as dishwater – he hems and haws.” You talk to a legitimate scientist, we always have doubts, “Well there’s science in favour, science against.” But you talk to dyed in the wool huckster, they know with absolute certainty that just the one simple thing you need to do, “It’s effortless, the pounds will drop off, the years will melt away.” You know, who can resist? I mean, your eyes glaze over, you go into a trance and you start reaching for your credit card.
The takeaway (36:10):
Feet, forks, fingers, sleep, stress, and love.
Disease Proof by David Katz
Aaron Carroll – Obesity intervention failures abound:
About 200 obese employees took part in a workplace wellness program to lose weight. Some were randomized with a financial incentive ($550) if they met their 5% weight loss reduction goal. After a year, the incentive was shown not to make a difference.
Perhaps a cultural shift is required, along with education.