Lab Cat

10 Feb 2008

Causes of Overweight

Filed under: Food, Nutrition — Tags: , , , — Cat @ 10:00 am

A commentary* by Gary Taubes in New Scientist puzzled me. He has forgotten the simple equation I was taught as a nutrition major:

E=Energy(in)-Energy(out)

If E is zero, your weight stays the same; if E is negative, you lose weight and if E is positive you gain weight. It really is that simple, but Mr Taubes says, in his introduction:

FOR the past century, the advice to the overweight and obese has remained remarkably consistent: consume fewer calories than you expend and you will lose weight. This prescription seems eminently reasonable. The only problem is that it doesn’t seem to work. Neither eating less nor moving more reverses the course of obesity in any but the rarest cases.

Mr Taubes argues that causality is the issue – what causes us to want to eat more. This, however, is still saying that we overeat. Even if hormones or a virus or addiction is responsible, if we consume more energy than expended we put on weight. We might not be to blame, but the truth is we are overweight because we took in more energy more than we burnt off.

It is not simple to lose weight. Losing weight requires a lot of effort and, most likely, an change in lifestyle. A change in what is usually quite a comfortable lifestyle. Losing weight is more than deciding not to eat a chocolate bar today. It requires the person to totally change how they approach food and exercise. They need to decide that they are going to change permanently, not just for the next month or so. Old influences will remain and keep on pushing you back to old habits. In fact, losing weight to keep the weight off, is not dissimilar from quitting smoking. The temptation to take up the old habits will always be there.

My story is that I never gained weight. I was one of the lucky ones with a fast metabolism. Then, after becoming a faculty member, I gained weight. I assume it was because I no longer spent long days walking around a lab. Instead I was sitting at the computer all day. I am more accustomed to American portion sizes, than I was in my first few years in the US. I also live in an area where it is more convenient to drive to the grocery (and other) stores – previously I would walk there or pass by on my bicycle on my way home. In other cities, I either had a significant walk (25 mins plus) each way or I cycled for the same length of time. I also was a keen walker (hiker in US terms) and would frequently spend Sunday in the hills around Yorkshire with friends. Somehow, I have not found an equivalent group of friends in my home town. As I have to make time to exercise, I do not do it often enough.

Perception of how much we eat and how we exercise is an issue that is frequently overlooked by writers including Mr Taubes. Thus, he ignores the fact that we perceive what we eat poorly; frequently eating more than we recall. I was glad to see, in the letters, that other NS readers had a similar reaction to Mr Taubes commentary. The first of these web letters states exactly the problem. Dieting does not work, because we do not keep to our diets.

In turns out, unfortunately, his commentary ends up being a plug for low carbohydrate diets. These diets were shown to be just as ineffective as low fat diets once there were enough food products available allowing us to return to our traditional way of eating, roughly three meals a day and snacks between. Initially, when the Atkins diet was first becoming popular, there was very little you could eat while following the diet correctly. Then, there were Atkins diet (or low carb) snack foods, which meant that we could eat in the traditional manner

He does make some interesting points that were made by Yudkin and others before:

… the consumption of refined carbohydrates, starches and sugars, all of which prompt (sooner or later) excessive insulin secretion. Insulin is the primary regulator of fat storage. When insulin levels are elevated, fat accumulates in our body tissue; when they fall, fat is released and we use it for fuel. By stimulating insulin secretion, carbohydrates make us fat; by driving us to accumulate fat, they increase hunger and decrease the energy we expend in metabolism and physical activity.

High sugar foods cause a “sugar rush” and then an opposite downturn in energy. A bit like taking drugs – you get the high, and unless you take more, you get the low. Even though this is a simplified view of the situation, but does imply that the constant consumption of sugary drinks would lead to insulin secretion being over extended.

Remember: If you want to lose weight, consume less calories than you use. You will need to be very honest about it and remove old temptations.

Footnotes

*Sorry, behind a pay wall:
Taubes, Gary 19 January 2008 “Comment: The great diet delusion”, New Scientist Print Edition.

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5 Comments »

  1. If one eat fewer calories than one expends then hunger is the consequence. Hunger is regulated by the body; why should humans be the only species on the planet that has to count calories? In a normally regulated body, excess calorie intake is burned by an increased metabolism, or is excreted.

    It is what you eat, not how much.

    Mr. Taubes has written several hundred pages on these topics and can assure he ignores none of what you claim.

    Comment by Geekay — 10 Feb 2008 @ 10:17 pm

  2. This strikes a chord with me. As a large woman, I can agree with the idea of food temptations being like smoking temptations (not that I’ve ever smoked or could – BLECK!) I am trying to make better food choices as of late, but the desire to save time by grabbing some fast food or to snack unwisely is something I really do deal with frequently.

    I also concur with the notion of us having poor perception about the amount we eat. I keep thinking I need to try a food journal to track what all it is I am taking in, but I am a little afraid of having the results in black and white.

    Comment by Lisa — 11 Feb 2008 @ 9:17 am

  3. Geekay,

    The problem really is that we are no longer listening to what our bodies are telling us. This means we misread when we are hungry or we think we are hungry when we are actually thirsty. Or similar situations – there is a whole field of psychology on this topic.

    I disagree with you on the fact that our metabolism speeds up or excess calories are excreted. Excess calories are converted to fat. Thus, I stick to my argument is that is is how much you eat, not what.

    Lisa,

    I offer encouragement to try keeping a food journal. At least then you have a starting point.

    Comment by Cat — 11 Feb 2008 @ 6:44 pm

  4. Lab Cat,

    As a food scientist, you must be aware of the work of Jules Hirsch and Ethan Sims? Their work has shown that weight regulation is nowhere near as simple as calories in – calories out (see summary here, and increasingly modern-day research is supporting their findings.

    Hirsch put his subjects on a very restricted (600 calorie) diet, but found that while the patients lost weight temporarily, their metabolisms decreased 24%, they suffered from the psychiatric syndrome semi-starvation neurosis, and nearly all of them regained all the weight they had lost, without exerting extreme efforts to avoid this.

    Conversely, Sims took normal-weight people and tried to make them gain weight. He found that the subjects had to consume up to 10,000 calories daily in order to maintain body weights 20-25% above their starting point, as their metabolisms essentially kicked into hyperdrive. Then, as soon as they returned to a normal diet they rapidly lost the weight.

    Further, I could give you dozens of citations for twin studies showing that BMI, adiposity, and waist circumference is 70-80% heritable, in addition to the Stunkard study mentioned in the above-linked article.

    This and many other studies show that most people have a set point around which they may fluctuate by 10-20 pounds, but beyond which their metabolism will adjust to maintain body weight within this range.

    Study after study has shown that diets don’t work – that 95-98% of dieters regain all the lost weight (and, often, more) within 5 years, and that dieting can actually have harmful effects on the body (see, e.g., this article).

    Study after study shows that fat people don’t eat or exercise any differently from thin people as a group – some fat people eat junk food while others eat low-fat vegan diets and exercise daily, and thin people do the same (see, e.g., this article).

    Now, those are the studies but I can also speak from personal experience. My entire family is overweight, and I have been overweight my entire life, despite dieting constantly from ~6 or 8 through my early 30s. I tried everything – 1000 calorie high-carb diets, Atkins, South Beach, you name it. At one point in my life I was able to get into the “normal” BMI range, but I did this by consuming 500-800 calories per day and running up mountains 2+ hours/day, 5-6 days/week. During this period I was thin, but I was also anemic, malnourished, and I damaged my joints. As soon as I began eating ~1000-1200 calories/day and only working out 1 hour/day 3-4 days/week, I regained all that weight.

    Similarly, a few years ago I went on a modified South Beach diet, eating a very low-fat, high-protein, whole-grain diet of ~1200 calories, and working out 1.5-2 hours 5-6 days/week – during this time I lost about 15 pounds, but was still just below the “obese” range according to the BMI. Today I’m a graduate student and don’t have as much time to cook or workout, but I still eat a low-fat, whole-grain diet of ~1500 calories and work out 45 minutes 4-5 days/week (plus walking all over campus and biking 3 miles each way to school), yet my weight falls in the obese category.

    How could calories in – calories out explain all of this? I suppose you could argue that people with slow metabolisms such as mine should just eat less, but what if that is more unhealthy than being overweight? Being thin required a 500 calorie/day diet with heavy exercise that left me malnourished, not to mention constantly hungry – and I simply don’t have 2 hours a day to exercise anymore. Why not instead acknowledge that people can be healthy at any size?

    Comment by kira — 17 Mar 2008 @ 4:27 pm

  5. Kira,

    Thank you for your comment and interesting links.

    I do not dispute the fact that genetics plays a large role in body type.

    The failure of diets is well known even if well hidden by the diet industry. Of course, the solution is more complicated than I have represented in my article, but reducing calorie intake or increasing calorie output are the only ways that body weight can be lost. It does not matter if you reduce fat, carbohydrates or protein. Gary Taubes was arguing that low carb diet was the way to go, where there is NO EVIDENCE that it is any better than any other diet.

    To be honest, if I ate 1000 calories/day I would be in semi-starvation neurosis, so it does not surprise me that happens when people are put on very restrictive diets such as those mentioned in the NYT article you link to. No one can healthily survive on such a small amount of calories. And naturally, when given the chance to eat without restriction, the weight is regained.

    I am, however, not convinced by your comment on physical exercise. [Your link goes to an article that explains why we gain weight as we get older.] You say you do not have time for two hours per day for exercise, but could you manage one hour or 30 min per day and then perhaps a whole day every other weekend? From my experience, I gained weight when I went from being a post-doc researcher (working on my feet in a lab for approx 6 h/day) to being a faculty member (all day in front of the computer). I am beginning to lose some of that weight as I currently work on my feet for 7 h/day three or four days a week.

    Once again , thank you for your comment.

    Comment by Cat — 18 Mar 2008 @ 10:09 am


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