Aug 02 2011

The Neuroscience Approach to Weight Control

The obesity debate rages on. I have covered this topic quite a bit on this blog – what factors contribute to overweight and obesity and what strategies are effective in maintaining a desired weight?

The outlook is fairly grim from the perspective that there are no easy answers or guaranteed techniques (from an intention to treat analysis). About 95% of all people who try to lose weight fail long term. Various diet revolutions (low fat, low carb, and an endless sequence of fad diets) have failed to produce results. Meanwhile, overweight and obesity in the industrialized world continues to rise.

Now a group of neuroscientists (Bradley M. Appelhans PhD, Matthew C. Whited PhD, Kristin L. Schneider PhD and Sherry L. Pagoto PhD) have weighed in on the debate in an article titled: Time to Abandon the Notion of Personal Choice in Dietary Counseling for Obesity? Not surprisingly, they take a neuroscientific perspective on weight control.

The essence of their article is that the “personal choice” paradigm of weight control has essentially failed (sound familiar?). It is simply too difficult to control eating with pure force of will. You can do it for a while, but not consistently enough long term. It takes just a moment of weakness to undo an entire day of self-control.

They argue that by understanding eating as a behavioral result of neurological processes, maybe we can come up with some strategies that will work.

They identify three primary neurological processes at work: food reward, inhibitory control, and time discounting. Food reward is probably obvious – the reward centers in our brains give us a happy dose of dopamine when we give in to our food cravings. We evolved in a calorie restricted environment and we crave calorie dense food – sugar and fat. They write:

Obesity has been viewed almost exclusively as a disorder of energy homeostasis in which overeating results from insufficient satiety signaling or amplified hunger signaling. However, research conducted over the past decade has demonstrated that the sensory experience of palatable food can easily override homeostatic controls of energy balance, leading to overeating in the absence of true physiological hunger.

In other words, we eat even when we don’t need the calories because food is just so yummy. Neurological speaking, the need for calories drives hunger, but in addition we evolved a pleasure reward response to the act of eating, and this alone can drive overeating. In this sense eating can be like any other reward-driven addictive behavior.

The next factor, inhibitory control, is our ability to override our food cravings. They describe, essentially, the neurological basis of “will power.” The authors write:

Dieters who consistently selected health over taste showed greater dorsolateral PFC (prefrontal cortex) activation when choosing the healthier options compared to those who more often selected taste over health. Further, there was evidence of functional connectivity between the dorsolateral PFC and brain areas associated with reward processing, consistent with the notion that the dorsolateral PFC inhibits the influence of reward on behavior.

Therefore we can look at our food choice as a struggle between the reward centers of our brain and the prefrontal cortex trying to exhibit control. The authors do not get into this – but other research shows that our ability to maintain self-control is reduced in many situations. For example, when we have already expended energy in other areas of self-control, we “reward ourselves” with a little overeating. Also, when we are sleepy or even physically exhausted, our inhibitory control is reduced.

So again, a long day of healthful eating can be undone by a moment of weakness when we are stressed, tired, or expended from others acts of self-restraint. Watching other people indulge will also lower our resistance through social pressures.

Finally the authors discuss time discounting:

A third factor that likely contributes to the low success rates of dietary interventions for obesity is the human tendency to devalue delayed rewards. Most of us would prefer to receive $200 today rather than $300 a year from now. This decision illustrates the fact that the brain discounts the value of money and other rewards over time, resulting in impulsive, short-sighted decision-making.

I would add to this another factor – denial and rationalization – which ties in to the other factors above. We want to eat the yummy cheesecake. But our resistance is finite, and may be compromised by many factors. Besides, we can deal with the consequences later – but the cake will taste really good right now. So we deny the known consequences of eating the cheesecake and rationalize our decision. We haven’t eaten that much today. We can afford a little cheesecake. We’ll just do some extra exercise tomorrow.


While I found the article very interesting, it isn’t really discussing anything new. The authors primarily discuss the neurological basis of what psychologists have already copiously documented.

I do like the approach, however, of looking at eating as a consequence of neurobehavioral factors. (This may be, however, because I tend to rely on intellectualization as a defense mechanism, and looking at behavior as brain activity is a great way to intellectualize our actions.)

The recommendations that the authors derive from this approach is to reduce the tempting foods in our environment. So, do not rely on continuous self-control, just don’t have a lot of calorie-dense food around the house. Also, limit buffets and other open-ended eating opportunities. They also advise stress management, as stress further drive overeating.

Again – this is all nothing new. But it is good to emphasize that trying to manipulate the food environment is likely to be more successful than navigating an environment that strongly encourages overeating with will power alone.

We also might extend this beyond the personal environment discussed by the authors to the social environment. This gets to the issue I recently discussed on Science-Based Medicine – to what extent should we use regulation to change the food landscape to counter the obesity epidemic.

I do think that this is where the conversation needs to be – not which magic combination of foods or nutrients will cause the weight to melt away without effort.

25 responses so far

25 Responses to “The Neuroscience Approach to Weight Control”

  1. roadfoodon 02 Aug 2011 at 2:41 pm

    One thing that was not mentioned here is how the human “fear center” can be pretty good at balancing the reward center. At my last doctor visit (about six months ago), my doctor went over the results of my blood test and told me that I was at the pre-diabetic stage. He also took the time to explain what that meant, what the possible short and long term consequences are, etc.

    I’ve been a pretty incurable sugary-snacker all my life (I really love chocolate donuts, and m&ms . . .), but it’s amazing how much easier it is to stop myself from making a run to the donut shop when I just think about what my doctor told me. The fear of becoming diabetic is a strong motivator.

    Of course, I realize that (probably? hopefully?) most people will never find themselves in my situation, and I’m not saying that doctors should engage in fear-mongering or anything. I’m just pointing out that, from a neurological basis, fear — even of some long-term consequences — can be a great balance to short-term reward.

    I also wanted to add my support to the notion of reducing the tempting foods in our environment. Whether one is motivated by fear or just using will-power, it’s far easier to pass by the donuts in the store that one time a week that you’re shopping, than it is to stop yourself from getting up and grabbing a donut from the cupboard during every minute of the four or six hours a day you’re at home knowing that those yummy donuts are in there, calling to you.

    Finally, extending my personal anecdote, I want to say that over the last six months I’ve lost about 25 pounds. I have not been on any diet, I have not been counting calories or anything, although my basic “strategy” (for lack of a better word) has been “calories in vs. calories out”. I’ve been eating more sensibly, mostly (but certainly not always) avoiding sugary snacks, and getting more exercise. I confess that I still eat fast food for lunch most days, but I have been working on making at least somewhat healthier choices and just cutting down on the quantity.

    For whatever anecdotes are worth, my case shows that you can lose weight and become at least a bit healthier (I have a home blood pressure monitor, and my BP is notably lower now than it was six months ago) without doing any specific diet and without denying yourself everything that you like to eat.

  2. daedalus2uon 02 Aug 2011 at 3:28 pm

    I can’t read the paper yet, but the neurobiological systems that make foods so yummy are under neurobiological control. How yummy a food is changes with the physiological state of the organism. That is why when you are hungry, lots of foods seem yummy and you could eat many of them. When you are not hungry those same foods don’t seem yummy and you don’t want to eat them.

    This is illustrated (in a different context) in this comic.

    The exact stimulus doesn’t matter, what matters is how physiology interprets the stimulus. If something with lots of sugar and fat is perceived to be yummy, it is yummy and will be yummy until physiology changes such that it is no longer perceived to be yummy.

    The problem with overeating is a control system problem, the control system that the body uses to regulate food intake has a bad setpoint. Until that setpoint is fixed, trying to control how much is eaten is going to be extremely difficult. If it takes eating 110 units to switch off the desire to eat but it only takes eating 100 units to restore energy consumed, then unless those 10 extra units are eaten, the individual will remain hungry. Being hungry while there is abundant food that can be eaten is difficult. People can control it, but if one fetishize not eating, then one can easily develop an eating disorder, which have the highest mortality of all neuropsychiatric disorders.

  3. TsuDhoNimhon 02 Aug 2011 at 4:42 pm

    The recommendations that the authors derive from this approach is to reduce the tempting foods in our environment. So, do not rely on continuous self-control, just don’t have a lot of calorie-dense food around the house.

    Oh yeah, leave the Oreos in the store so they don’t end up on the hips! Don’t buy them “for the kids”, because they don’t need them either.

    Decades ago (early 1970s) I did diet and nutrition counseling at a free clinic – mostly because I was the skinny one with a lot of free time during clinic hours.

    I inadvertently developed several useful modification techniques that worked for about half the clients:

    Food journals (as long as the client was honestly reporting) helped identify where the weak points and easy wins would be … the woman who was eating 3 gallons of ice milk a week was encouraged to stop buying ice milk, and instead, take the price of a scoop of her very favorite flavor and walk to the ice cream parlor and enjoy it once a week. Just enough for ONE scoop, and if she wanted more, she had to walk home and get the price of another one.

    Recipe modification to trim calories without losing flavor worked well too. Instead of boiling the greens with 1/4 lb of fatback, we’d switch clients to steaming them and sprinkling a couple teaspoons of diced and rendered fatback on the greens for flavor.

    Oddly, encouraging “eating outside the box” helped … try a restaurant with a cuisine you had never tried, a recipe you had never cooked, a spice or herb you didn’t usually use.

    “Luxury food treats” substituted for comfort food, such as fresh raspberries instead of the equally priced large bag of chips.

    Buffets will work OK if you take a tablespoon of everything and sample it all. The flavor variety and small portions tend to satiate your taste buds.

    The best countermeasure to the “I’m not losing enough weight” impatience blues was a large backpack and bundles of magazines in 10, 5, and 1-lb packets. The client would put on the backpack and I added enough magazines to equal the lost weight and had them walk around the clinic and up and down the stairs. It made a slow, nebulous loss very concrete, especially when they were in the 30-50+ pound category. Most of the clients couldn’t pick up the backpack, or stand up from a sitting position with it on … it was impressive.

    A 24-hour fast (just one) so they could find out what hunger pains really feel like, as opposed to “gee that sounds good” whims.

    What didn’t work was handing them a diet sheet and saying “eat this”. It never does.

  4. TsuDhoNimhon 02 Aug 2011 at 4:47 pm

    @roadfood … the same small changes that put it on can take it off.

    My brother-in-law lost 15+ pounds in a few months with ONE simple behavior modification. He agreed to either eat OR watch sports on TV, but not both. If he wanted to eat, he had to get up, turn off the TV, go to the table and focus on the food he was eating. Eat it and pay attention to the flavor.

  5. Bronze Dogon 02 Aug 2011 at 6:38 pm

    I’ll be working on a few tricks, myself, mostly cutting down on portions.

  6. SARAon 02 Aug 2011 at 6:55 pm

    ” to what extent should we use regulation to change the food landscape to counter the obesity epidemic.”

    I worry about this. Suppose we go so far as to ban certain food. This leads to black market, which leads to illegal use, making every day people into criminals. See marijuana or prohibition.

    While I doubt if we go so far as to ban certain foods, it almost becomes a ban if we tax them to the extent that they become luxury items. In those cases, black markets blossom as well.

    I don’t have any real data on these thoughts, just thinking out loud (or in writing). I wonder if high prices has led to a decline in smoking? I do know it is mentioned when my friends decide to quit, but it doesn’t seem to the primary factor. Usually its health that motivates the decision. Its almost like they think of the extra money as a bonus, not the original motivator.

  7. billysixstringon 02 Aug 2011 at 6:59 pm

    So you think that the conversation should instead be on which magic combination of regulations will cause the weight to melt away without effort?

    This seems to border on the Nirvana Fallacy.

  8. daedalus2uon 02 Aug 2011 at 7:05 pm

    If the problem is in a neurological setpoint (which I think it is), regulations won’t have the desired effect. It isn’t an “addiction” to food, but if your “food eating setpoint” tells you to eat more food, it can be very hard to resist.

  9. rjblaskiewiczon 03 Aug 2011 at 1:19 am

    Price food by the calorie. 🙂

    I’ve made a point of not bringing large portions into my apartment, because they will disappear. Every day, I buy my day’s food. But when I go out, it’s the massive restaurant portions that get me every single time.

    I deserve a famine. I’ve been preparing for it for years.

  10. Mlemaon 03 Aug 2011 at 3:48 am

    I’m with roadfood: fear is a great motivator. Show people the real consequences of being overweight. Show them some autopsy materials from obese people with cardiovascular disease. Have them visit dialysis patients who have developed kidney failure from type II diabetes. Or blindness from diabetes. Or amputation from diabetes. Talk to the family members of someone who died an early death from obesity.
    It’s so much easier to change your diet when you’re really scared of what might happen if you don’t.

  11. eiskrystalon 03 Aug 2011 at 4:09 am

    I have never thought of sweet food as a reward particularly. Is consciously making it into a reward a problem in itself do you think?

  12. ziggyon 03 Aug 2011 at 7:11 am

    If only crystal meth was legal… lol

  13. SteveAon 03 Aug 2011 at 7:29 am

    roadfood: “but it’s amazing how much easier it is to stop myself from making a run to the donut shop when I just think about what my doctor told me.”

    Reading the grotesque account of a magazine writer’s brush with lung cancer*, finally convinced me to quit cigarettes (and I was a very dedicated smoker).

    Sometimes it doesn’t take much to snap us out of bad habits. We tend to think our behaviours become so ingrained over time that they will be impossible to change and it’s that belief that puts many people off the attempt.

    In my experience most bad habits quickly crumble in the face of determined opposition. Often it helps to change other behaviours that support the habit, for example I always smoked when I drank in bars. So when I quit I stopped going to bars for six months.

    If you’re trying to lose weight, give yourself a break and stop buying the snacks that you promise to ration out to yourself over a week (then eat in an afternoon). Cut them out entirely and you quickly start to forget about them. Believe me, it’s easier than it sounds.

    * it didn’t end well.

  14. CWon 03 Aug 2011 at 8:33 am

    This is why I’m hopeful that human ingenuity can help provide safe alternatives to unhealthy eating. Alternatives that provide equivalent comfort and pleasure.

  15. Ben-on 03 Aug 2011 at 8:42 am

    Shouldn’t we simply apply the same approach with eating we apply everywhere else when our perceptions misleads us? That is to _quantify_ what we eat in an objective way, instead of ‘guessing’ and following ‘moods’?

    Everyone is comfortable using kitchen scales when baking or doing cooking recipes to not screw up in the process, yet few bother to quantify what they actually swallow. Instead everybody relies on some ‘feeling’. That’s fine for as far as it can take you; but if your guesswork is off, don’t guess! Be objective.

    The good old virtues of engineering, which gave us mechanical flight and robotic assembly lines: measure, adjust the variables, close in on your goal. Done.

  16. roadfoodon 03 Aug 2011 at 1:50 pm

    SteveA: “Sometimes it doesn’t take much to snap us out of bad habits. We tend to think our behaviours become so ingrained over time that they will be impossible to change and it’s that belief that puts many people off the attempt.”

    Yes, I want to second this. As I said above, I’ve been a chronic snacker for all of my adult life (I’m over fifty, by the way). I pretty much always had something on hand (cookies, candy, potato chips, crackers), and would partake usually multiple times a day.

    After my doctor visit six months ago, I just decided that I needed to cut way, way down on snacking and sweets (I didn’t have my head in the clouds so much as to think that I could just stop snacking entirely). I had never before really, seriously decided to do that, and because of what I’d always heard about other people’s experiences at denying themselves something they’d always enjoyed, I expected it to be difficult. I saw a future of having deep cravings for those chocolate donuts, and having to summon vast amounts of willpower to fight it.

    The reality has been that, while I do “miss” the donuts and m&m’s, I’ve never really found myself experiencing a deep craving that required effort to stave off. It’s really been far easier than I thought it would be.

    I do still snack, but less often and more healthily. An apple; unsalted almonds; rice crackers. To satisfy my desire for sweet, an 80-calorie pack of fruit snacks. Sure, they’re a little fruit and mostly processed sugar, but certainly one pack of those is better than a half a box of mini-donuts. Without *something* unnaturally sweet, I probably would have a harder time with m&m cravings.

  17. kikyoon 03 Aug 2011 at 1:58 pm

    “So you think that the conversation should instead be on which magic combination of regulations will cause the weight to melt away without effort?”

    Not necessarily regulation – perhaps understanding the neurology involved will just lead to better education/advice when it comes to weight loss than what we currently have.

    Another part of it, I think, is the psychology involved. Because of the “calories in, calories out” metric, there is a widespread perception that stereotypes overweight people as universally lazy, self-indulgent or lacking in will-power because of the perception that they cannot make themselves or do not want to simply eat less and exercise more.

    It is a lot more complicated than that, as Dr. Novella has done a good job of exploring and unfortunately, with many people I have seen the above stereotyping also lead to a feeling that because of the perceived negative personality traits, it is also okay to “shame” or persecute overweight people based on the feeling that doing so will motivate them to lose weight. This is about the worst approach to take and is an extremely harmful way to approach the problem. Unfortunately the current focus on “childhood obesity” rather than “childhood nutrition/health” adds to this problem by demonizing children who are not at fault and erroneously sending a message to young children that weight is the number one determiner of health and healthy lifestyle. If you look at eating disorder statistics among increasingly younger people it is pretty easy to understand how dangerous this type of message is.

    I am so glad to see studies like this because I think that the current approach to this problem is about the worst way to go about solving a health problem (by singling out a specific subset of unhealthy people who are easily identifiable on sight as if they are the sole and only unhealthy people dragging the rest of us down) – particularly when and individual’s mental state plays such a big part in addressing the issue. Hopefully getting a better understandinfg of both the physiology and neurology involved can help us formulate better approaches to nutrition and health for everyone.

  18. PhysiPhileon 04 Aug 2011 at 11:18 am

    “there is a widespread perception that stereotypes overweight people as universally lazy, self-indulgent or lacking in will-power”

    This is an argument from final consequences mixed with a straw man. First, you use an absolute (universally) when we should be speaking in relative terms and is not a part of the opposing argument – which makes it a straw-man. Are people who are overweight or obese lazier, more self-indulgent, and have less will-power than normal weight individuals. People who are overweight and obese are less active and I believe activity is related to laziness, ergo, I would argue overweight/obese people are lazier than normal weight individuals. I’m not sure how you would measure will-power or self-indulgence, but I’m sure a trained psychologist could think of a good metric.

    “because of the perception that they cannot make themselves or do not want to simply eat less and exercise more.”

    You use the word perception as though their perception doesn’t reflect reality. My logical deduction is as follows:

    Assumption: One desires to obtain a more healthy weight

    Assumption: In order to lose weight, one must change a fundamental behavior

    Assumption: To change a fundamental behavior one must have high will-power

    Argument: If one has a high will-power they will alter the fundamental behavior of eating

    Argument: If one is not altering this fundamental behavior, one does not have high enough will-power.

    The second part – “do not WANT to simple eat less” – is a straw man. Most people know that if one had a choice to be overweight or normal weight, one would choose normal weight.

    “If you look at eating disorder statistics among increasingly younger people it is pretty easy to understand how dangerous this type of message is.”

    I looked at the statistics and disagree with your analysis. A review in the International Journal of Eating Disorders, gives the prevalence of young girls with anorexia nervosa at 0.3% and bulimia nervosa at 1% and an incidence of only .008%*. Whereas, according to the CDC, 17.6% of adolescence between ages 12 to 19 are overweight from years 2003 to 2006. This is an order of magnitude difference and warrants much more focus than eating disorders.

    “as if they are the sole and only unhealthy people dragging the rest of us down”

    Again, you are throwing around absolutes almost to make it easier for you to argue against this non-realistic person who only thinks in absolutes. No remotely reasonable person would say overweight/obese individuals are the sole and only unhealthy people. One may say that obesity is the highest contributor to human malady. I wouldn’t think that an unreasonable statement since heart disease causes about half of all deaths and obesity is strongly correlated with heart disease and we have an obesity epidemic.

    * Hans Wijbrand Hoek (2003). Review of the prevalence and incidence of eating disorders.

  19. Dan Royon 05 Aug 2011 at 7:31 am

    For adults with kids I try to preach the Fear/Joy argument:

    “Hey buddy, wouldn’t it be great to give yourself the chance to see your own kids grow up, talk to your grandkids and even possibly their kids? And as a bonus add another 10-20 healthy years to your own life?”

    When this argument, especially about the kids and grandkids, sink in, it’s far easier to walk past the donuts.

  20. SteveAon 05 Aug 2011 at 8:24 am

    PhysiPhile: “I would argue overweight/obese people are lazier than normal weight individuals.”

    I think there’s also something missing intellectually. It’s not exactly stupidity, it’s more of a blind-spot that disregards long-term benefit (weightloss) in favour of short-term gain (doughnut).

    There were some experiments reported on recently where children were given the choice between one marshmallow now, or two in fifteen-minutes time. The children who chose the single marshmallow in front of them later went to do significantly worse than their more patient playmates. As far as I can recall performance was measured against academic record. I wonder if the ‘want one now’ kids were also worse off physically?

  21. mufion 05 Aug 2011 at 9:44 am

    This is an order of magnitude difference and warrants much more focus than eating disorders.

    On a national level, that may indeed be true (although I suspect that the rate of eating disorders is actually higher than what your source reports – particularly in the US).

    However, I’m far more worried about this:

    “The mortality rate associated with anorexia nervosa is 12 times higher than the death rate associated with all causes of death for females 15-24 years old.” *

    than I am about this:

    “Life expectancy of a moderately obese person could be shortened by 2 to 5 years.” *

    Why? Because both anorexia nervosa and moderate obesity coexist in my household (not in the same individual), and it seems clear which problem poses a more serious and immediate threat.

    What’s more, the anorexic mind thrives on the notion that fat is a symptom of laziness and other kinds of moral failure. So, my use of that kind of language around my daughter would seem a perfect way for me to hinder her treatment and recovery.

    Naturally, I don’t appreciate it when others do so.

  22. mufion 05 Aug 2011 at 9:51 am

    PS: I hope it’s clear that I’m not opposed to devoting more national resources to reducing obesity rates. All I’m trying to say is that it matters to me how you do it.

  23. PhysiPhileon 05 Aug 2011 at 4:20 pm


    I think you brought up some good points. I can relate to you because my immediate family has a high number of mental illnesses ranging from schizophrenia, bipolar disorder, to severe depression. Just last month I thought I killed my girlfriend because I asked her to go check on my mom who was hiding in a shower while my brother was “protecting” her from demons with a sword only to find out he was looking for a gun and I realized he may confuse my girlfriend with a demon and shoot her (luckily the cops got the house before she did).

    There are some things that, although may be true, I would NEVER say to someone with mental illness. This blog often speaks about topics that are taboo and if I were to bring these topics up to my family, they would be insulted and unappreciated. And because of the nature of this blog, I am more frank so I apologize if it comes across as indifferent – that is certainly not the case. In general, I do not think we should stop speaking about possible causal relationships because it may cause a negative outcome in someone else. For example, I know depression increases the risk of suicide but, in my experience, that fact only makes the depressed person more depressed. This does not mean we shouldn’t speak of the link between depression and suicide but should be careful who is listening.

  24. mufion 05 Aug 2011 at 4:52 pm

    Thanks, PhysiPhile. No hard feelings. Just speaking my mind, as usual.

  25. Kultakutrion 25 Aug 2011 at 2:34 pm

    I find the insight interesting. The article is behind a paywall but I’ll ask for it when I drag myself to the library (too hot to get out, I’m not that overweight).

    I’m overweight myself. 15 kilos caused by antipsychotics I didn’t need (the so-called psychosomatic indigestions stopped when I cut on milk and discovered lactase), 15 kilos are my own doing, I admit it. Those 30 kilos ago, I was maybe five kilos above my anorexic weight. Hint hint wink wink. So, if I’m shown a clogged artery of some deceased obese person, I may be scared shitless, right, but there would be a bit of side effects – I’d simply stop eating. I have the willpower not to eat and I still get a nice high from starving myself. I don’t have the willpower to eat normally so I’m struggling to balance weight loss with reasonably normal eating and no obsessing about control.

    I don’t feel obliged to explain this to any random idjit who comments on my weight, and in general, I care a damn about idjits, but what I find disheartening is that the health care professionals don’t listen even when I explicitly tell them. It took me five orthopedists before I found one who would admit that losing weight would improve my knee problems but he proceeded to get actual x-rays to see what’s going inside instead blaming everything on my excess weight and telling me to lose it and to get some ibuprofen should it hurt much. Which is sad.

    Another sad thing is that overweight people are perceived as some lower sort of humans. Lazy, no willpower, ugly, they sweat a lot and stink… go figure. I find it extremely offensive from a random stranger. Yes, there is a sort of people who think that a fat woman, and even worse, a blonde one, is some sort of dumbass that needs to be told what to do with her life. I wonder how much dopamine their brains produce upon offending people.


Trackback URI | Comments RSS

Leave a Reply

You must be logged in to post a comment.