The Skeptic community has some very talented people who use a variety of media to enlighten others, and one of my favorite websites that does "education through art" is the web comic Ape not Monkey. I was actually pondering how best to answer a charge about how it was "completely wrong" to say someone could eat [insert unhealthy food here] and still lose weight, when another friend pointed out to me that this comic was doing a series food labeling and diet. I like what the author has done so far as linked above, and am looking forward to seeing the rest in his series. It looks like he's already started on a rant about how many things impact our metabolism and how claiming foods have "negative calories" is, at best, a distortion of our complex metabolic processes.
Anyway, the charge that no-one could lose weight eating "crummy" food, and related charges that I've been reading lately stating that "calories in/calories out" doesn't work, reminded me of this post that I had written commenting on Brian Dunning's post on Skeptoid (who did the research for the Ape not Monkey posts!) where Brian did just that--lost weight by controlling his calories. He also linked to some other self experimenting people who had lost weight while eating twinkies, etc, and did acknowledge that what he was doing was anecdotal, but at the same time scored several points for the skeptic community. I pointed out that none of are exempt from the First Law of Thermodynamics as well, but I also pointed out that some of us do benefit from using a few more behavioral attributes to stay on track.
So we have case studies that indicate people have lost weight, and kept it off, by merely controlling their calories, and then we have case studies of people who were not able to achieve their body weight until they followed a paticular kind of diet. Then, of course, we also have more recent studies (not just observational) that indicate people following a low carb plan do actually seem to experience basal metabolic changes, and studies like the Body Weight Simulator that indicate that the very act of losing weight can change our metabolism in ways that we didn't necessarily expect. So what is a Skeptic suppossed to do?
First of all, we need to ask what other health goals we are really trying to accomplish here, and by that I mean that not everybody is trying to "just" lose weight. Most of the people I work with are trying to control their blood glucose and/or avoid Type 2 diabetes, lower their LDL and/or triglycerides, lower their blood pressure, prevent cardio vascular disease (or in the case of one of my new patients, prevent having stroke number 6!). Oh yeah, and they want to lose weight too. Granted, I work with a population known for the mulitiple medical problems, but I know they are not the only people out there with what we call "co-morbidities" or sometimes "weight-related illnesses." So, for example, maybe are a person with diabetes and you are someone who actually makes a point of staying within your calorie limit every day. You've been losing weight slowly, but your doc just told you that your bloodwork isn't looking so hot, so you decide to test your blood sugar more often, including before you eat after you eat. You test your blood glucose before you eat and it's 115 mg/dL (which is not bad, could be better) and then you eat your little bowl of oatmeal, and about an hour later you test and you find you blood glucose is now 225 mg/dL! (I would love to see it less than 180, and that's still aiming for a higher goal than I want.) You start testing at other meals and you still see higher readings than you want, but you were staying within your caloric limit and losing some weight! So, you are probably meeting your goal of losing weight, but you certainly aren't meeting any blood glucose goals, and your related problems of blood pressure and triglycerides probably don't look so hot either. This means that 1) you need to do some goal revision and add "bring my fasting blood glucose levels to 70-100, etc." and 2) realize that "what" you eat really is as important as "how much" you eat, especially for people with insulin resistant related problems (blood pressure, type 2 diabetes, prediabetes, high triglycerides, etc).
Second of all, while any weight loss is going to help someone who is morbidly obese, some people are worried about how much of their body weight is fat mass or lean body mass (muscle and all the other non-fat parts), a ratio that we usually call "body composition." If you have achieved a weight that you want, but you still have a "spare tire" around your middle, chances are you've still got more body fat than what is healthy for you. Or, most common in people who lose weight very quickly, the muscles in your arms and legs actually look shrunken, a condition we call muscle atrophy or wasting. If you didn't lose your spare tire, you are all at a higher risk for diabetes, cardio vascular disease, etc, and if you lose muscle mass you might be more at risk for developing bone disorders later in life and you can still have more problems with insulin resistance. I think that "losing excess body fat" is a more accurate description of what people really want to do, and most people would probably want to add "keep/build my lean body mass" at the same time. "Change my body composition" would also be a fairly accurate phrase as well. I do not like the term "lean out" because it sounds too much like an advertising gimmick, but that is my curmudgeon coming through. Moral of the story here is that you probably want to preserve your lean body mass and lose extra fat, and the composition of your diet can make a difference as well as taking in less calories. If you don't consume adequate protein (and a lot of my patients don't), you are more likely to lose muscle along with the fat. If you don't do any kind of resistance training, you are more likely to lose muscle along with the excess fat. If most of your calories are coming from carbohydrate, and you have a history of insulin resistance, chances are you are going to have trouble losing that spare tire because you are elevating your insulin levels, and the glucose that you do not "burn" for energy gets stored right there in your belly (you'll see something similar if you "save up" your calories so that you can have a six pack of beer every night). Once again, I just simplified a very complex interplay of a variety of hormones, insulin is just one of those. You can read a little more here.
Third, we do have to think about the way the basal metabolism does change when we reduce our calories. At the risk of getting too anecdotal here, I have worked with people who had to lose a certain amount of weight just so they could have Gastric Bypass Surgery. Yeah, it sounds weird, but we had some people that had so much extra abdominal fat that the surgeon could not perform the surgery, and a lot of them had addtional fat deposits in their liver which was also obstructing the surgeon, so losing weight would help remove the obstructions. So, people would lose the required amount of weight, have the surgery, which for some was a life saving procedure, and then of course they would have to deal with the sneers, even from people in the medical profession, about how "well if you can just put less in your stomach now, why can't you do it forever?" Well, my fellow skeptics, one of the reasons is that cutting the calories alone on average only helps people lose about 10% of their weight (Link). Fine if you only wanted to lose from 205# to 185#, but if you are 330# and you are now stuck at 300#, you probably still have some health problems going on and/or still being a little hard on your joints. There was also a study done by the NIDDK that resulted in the creation of the Body Weight Simulator that shows the changes that your metabolism can go through when you reduce your calories. So for some high risk individuals, having major surgery and inducing malabsorption is what that person and his/her physician has decided is the best course for them (and really, the sneering doesn't cause someone to lose weight). Now, there is some evidence that people on carbohydrate controlled plans can actually alleviate some of the metabolic changes and go beyond that ten percent (Link), but then there are still those who have been overweight for so long that they still find themselves "stuck" at a higher body fat than they want (and my friend Georgene actually details her experience in her book). Of course, your body fat percentage is not the only marker of your health either. Some people do have extra and maintain excellent lipid profiles, blood glucose control, and blood pressure control, and they are (gasp!) even satisfied with how they look.
Fourth, losing body fat is not the hard part, keeping the weight off is. That's why so many people are willing to brag about their latest diet, or "magic weight loss tool," when they first start, and then, in the words of Clemens at Ape not Monkey, "I hate it so much!" So, you actually want to find a plan that you can stay with and not be hungry and yelling at people all the time. I happen to prefer the carb controlled approach because by not elevating your insulin levels you can control your appetite better, but not every overweight person is insulin resistant and so that may not be the best approach for everybody. And then there was a friend whose diabetes is currently controlled with Victoza and (mostly) diet, who asked me about going on insulin as every time she eats rice, etc her blood glucose goes way to high. I tried to gently direct her to a more diet controlled approach, but, in her words "I want to be able to eat rice when I want too!" Not my way of approaching things, but as her main goal is to keep her blood glucose controlled AND still eat rice when she wants to, I can't fault her for that. And then there is a related, but albeit more difficult to quantify, issue of "how I feel." Some people, when they spend all day eating pop-tarts they just feel more tired (and if your blood glucose levels are swinging, you may not feel so hot). Staying with your new plan is hard enough, why add more misery to your life by continuing to eat things that do seem to cause a noteable change in how you feel?
Fifth, I know some of you are whining about keeping track of your caloric intake, even if you've got a handy smart phone app for it. I also saw someone complaining on the internet about how "our ancestors didn't count calories, so why should we?" Well, even if you don't count calories (or exercise portion control, as I also call it), you are still going to be reading a bunch of labels for carb content and hidden whatever else you are trying to avoid, so you are still doing the same amount of work. Also, true, those who limit themselves to protein/olive oil/vegetables (and are ok with that) don't really have much to think about, but some of the rest of us do actually want some of those indulgences (like wine!), so you better be keeping track of the calories and portions to make sure you are not indulging too much or too often.
In summary/take home message--both how much and what you eat are going to help you reach your health goals, it's not an either/or thing. You need to ask yourself the following:
1) What kind of foods/quantities of foods will help me achieve my other health goals?
2) Do I care about my body composition right now?
3) Will I be content with just ten percent weight loss or do I need to try to go beyond that?
4) Can I stay with some version of my diet for the rest of my life and, at the very least, be content with this?
5) Am I watching my portions of everything!