Studying Weight Loss
Katherine from Low Carb Freedom has a nice piece on a recent study presented by Brown University that purports to show that low-fat diets are more effective at weight loss for the long haul. I saw this article yesterday but hadn't gotten around to commenting about it I guess because it comes with the refrain that we've been hearing for months now - "low carb diets are on their way out." There are so many articles with those headlines and yet all the people I know who have been doing low-carb plans are still doing them.
The problem with these studies is that they are flawed from the get go, and so whatever they allegedly show is really nonsense. As Katherine mentions, they often deem "low carb" as simply being lower then the ridiculously high average that has been the case in the American diet, at least until recently. So instead of 300 grams of carbs per day, the dieters are consuming 100 grams. But as anyone who has read a low-carb book knows, 100 grams is much higher than what a low-carb dieter would eat unless he or she were on the maintenance phase after losing all their weight. This is doubly dumbfounding because so many critics basically paint low-carb as NO-carb diets. This all may seem like an abstraction, but the fact of the matter is that much of low-carb theory is based on keeping the level of carb consumption at a point where it has minimal effect on insulin. If you go slightly over, you end up with it not being that effective. Sure eating 100 grams of carbs is better than eating 300 grams, but for many it’s not going to allow them to lose much weight, if any.
As Katherine notes, the actual text of the study is not available and so we don’t know whether they accounted for various variables. Let’s look at just a few of these. Did the dieters all have the same level of exercise? Exercise (what type and how long) play a significant role in how a person loses weight. Did they all start at roughly the same weight? Those who have more to lose to begin with tend to lose more weight on average, no matter the diet. What was their dieting history prior to this study? Frequent, “yo-yo” dieters often have a much harder time losing weight because, it is though, they have conditioned their metabolisms to hold onto more excess fat for longer. What were the dieters eating? While the news report notes the macronutrient levels and caloric totals, the types of fat (MFA vs. SFA, etc.), and the vitamins and nutrients in natural food as well as the chemicals and preservatives in processed food, all have effects on the overall picture. Dieters studied from similar ethnic and racial groups? Genetics have been shown to effect how the body metabolizes things. Those whose ancestors are from hot climates generally have a much greater potential towards insulin resistance for example. Was the amount of water among the two groups tracked? In terms of weight loss, was only the actual weight measured or was their any effort to determine how much of that weight was fat and how much was muscle, water-weight, etc.? And we haven’t even talked about the murky waters of psychology and how a person’s attitude effects how well they adhere to the diet, stress levels, etc.
The dieters were participants in The National Weight Control Registry, which is a voluntary and open registry, but you need to have maintained a 30-lb loss for over a year. So this eliminates anyone who has lost under 30 lbs, even if that’s all they needed to lose. None of the results are verified by doctors, they simply ask participants to fill out a form, so even the validity of the data is in question.
The ONLY way, as far as I can see, to get anything approaching usable data is to take many individuals and isolate them in a setting where you can completely control as many of the variables as you can. You compare only individuals who are about the same age, race, ethnicity, diet history, and starting weight. You give each participant within each group the same exact food. You make each of them do the same exercise routine, etc.
Even doing something like this you’re going to run into differences based on genetics which for the time being we won’t be able to easily differentiate. Mapping the Human genome will eventually produce a much tighter understanding of at least that one facet. Sleep levels have also shown to be important in weight loss and you can’t make people sleep the same amount necessarily. Stress can also have an affect and while you can remove stress from an environment, you can’t control what inherent issues may crop up from a participant being away from their family, or being with other people that they may not get along with, or simply other emotional issues people will bring with them to such a study.
Studies of the kind I mention have been done, but they are few and far between and relatively small due to their expense. If we are really serious about getting to the bottom of some of these questions, though, such studies with larger numbers need to be funded more because it will be the only way to get close to having some degree of confidence in what the best way to eat is, and I suspect even if this were to happen we would get conclusions that were open to interpretation and which varied based on one’s age, heritage, and dieting history. In the mean time, my advice would be to just read as much as you can about different diets and fitness plans and try each, recording how easy it was to lose weight, how long you are able to keep it off, how the diet impacted your energy level and other health factors that are measurable (blood sugar, insulin, triglycerides, etc.), and how it changed your body fat percentage, not just your weight. Ultimately we all have to be our own study – both the researcher and the participant – in order to come up with what works best for us. Getting bent out of shape or even taking at all seriously a “study” such as the one Brown University presented, is pretty much pointless.
UPDATE: There was a press release today from Catherine LaCroix of Low Carb Living Magazine in which she got a comment from the presenter of the study, Suzanne Phelan, Ph.D., Assistant Professor of Human Behavior at Brown University, that the headlines stating that the study showed that low-fat was more effective than low carb was "misleading." Additionally, LaCroix uncovers that the differential in calories that may have caused less weight gain was not from fat per se but from "junk food."