Tag Archives: weight loss

Metabolic Advantage

The concept of a metabolic advantage with low carb diets is hotly debated. A quick MegaSearch shows hundreds of articles and blog posts, including some spirited debates. So what is this so-called metabolic advantage?

Dr. Michael Eades explains it this way:

When two groups of subjects both eat the same number of calories (but provided by diets of different macronutrient compositions) and maintain the same activity level, yet one group loses more weight than the other, the group losing the greater weight is said to have a metabolic advantage. Or, more specifically, the diet driving the weight loss is said to provide a metabolic advantage.

The debates among doctors, researchers and advocates sometimes gets heated. I won’t post a link to the profane and, in my opinion, irrational posts by Dr. Eades’ opponent in that particular debate, but Dr. Eades includes it in his blog post.

The literature does show an apparent metabolic advantage in studies. Just this week (March 2, 2011) the American Journal of Clinical Nutrition published a new study, Short-term weight loss and hepatic triglyceride reduction: evidence of a metabolic advantage with dietary carbohydrate restriction:

The aim of this study was to determine the effectiveness of 2 wk of dietary carbohydrate and calorie restriction at reducing hepatic triglycerides in subjects with NAFLD [Non-Alcoholic Fatty Liver Disease].

NAFLD, or “Non-Alcoholic Fatty Liver Disease” is a condition where the liver “gets fat”, resulting in reduced liver function. It is growing at an alarming rate, with some pointing towards increased fructose consumption as a likely cause (fructose is metabolized by the liver).

Like other studies, this one notes a “metabolic advantage” with a low carb diet:

Two weeks of dietary intervention (≈4.3% weight loss) reduced hepatic triglycerides by ≈42% in subjects with NAFLD; however, reductions were significantly greater with dietary carbohydrate restriction than with calorie restriction. This may have been due, in part, to enhanced hepatic and whole-body oxidation.

The phrase “significantly greater with dietary carbohydrate restriction than with calorie restriction” is the evidence the researchers note as a “metabolic advantage.”

The hotly contested debate will continue, of course, but as evidence mounts that lower carb diets result in greater weight loss and less hunger than calorie reduced calorie diets, can the debate sustain itself for very long?

Eat Less, Move if You Like

We have heard the admonitions to “Move More, Eat Less” from fitness gurus and other scoundrels. The implication is that if you are fat, it is your fault. “Get up off the couch, you lazy bastard.”

The problem with “Move More, Eat Less”: it is a lie.

It seems logical though, doesn’t it? After all, you rarely see fat marathon runners. But, as Gary Taubes has noted, you also rarely see short NBA players. And no one thinks playing basketball makes you taller.

What does science say? You might be surprised.

Dr. Briffa recounts a conversation after a lecture:

Over lunch, after my presentation, I was talking to the one of delegates who expressed doubt about my ‘opinion’ that aerobic exercise does not generally promote weight loss. On what basis? He told me that there are no overweight elite marathon runners. So, marathon running must lead to weight loss.

So commonly and strenuously have we had the idea that aerobic exercise drummed into our psyches, that perhaps it’s no surprise that this man held this opinion. However, the thinking here is obviously limited, and in more than one way.

[…]

In other words, I was asking him to consider that people don’t get thin because they are marathon runners, but are marathon runners because, at least in part, they are thin.

(Also, I did point out that my view on exercise and body weight is not really an ‘opinion’ – it’s actually based on quite overwhelming evidence in the scientific literature.)

This is not a new revelation. Exercise can bestow many benefits on the individual, including better overall health. It just won’t lead to weight loss. Science has known this for a long time.

Dr. Briffa points to a recent study looking at activity levels and obesity in children. If the study just looked at fat kids, and measured their activity level, it would show that they tend to be more sedate than their skinny counterparts. You would think that validates the belief that the active kids burn off more calories and are therefore thin. But this study is different; it looked at activity levels as the kids became obese.

The study followed 202 seven year olds in Plymouth, England for three years. They were drawn from 40 different schools, and 53% were boys. It was a good mix of children. There was no “intervention” in this study. They didn’t counsel them on nutrition, exercise, or anything else. Over the course of the study they measured their height and weight, and had them wear special activity meters for seven day periods.

Some segment of the population will gain weight over any three year period. Some of these kids did just that. And it is with these kids that the interesting facts come out. Comparing the physical activity to weight found there was no correlation between physical activity and weight gain. The kids who gained weight did not reduce their physical activity first. But there was something else found. After the kids gained weight, physical activity decreased.

That’s right: active kids got fat and then got less active. They didn’t get fat because they were less active.

As the study puts it:

Physical inactivity appears to be the result of fatness rather than its cause. This reverse causality may explain why attempts to tackle childhood obesity by promoting [physcial activity] have been largely unsuccessful.

For most people, especially obese people, exercise stimulates hunger. And what you eat is, in our opinion, more important than how much you eat. In a typical western person’s daily life, an increase in exercise often leads to increased food intake … and usually the worse food is used to “reward” the successful completion of good healthy exercise.

Part of the reason is simple math. So let’s say we decide to cycle for exercise. Instead of driving to Starbucks, we’ll ride our bicycle. And the Starbucks isn’t really that close! It will take us an hour to get there, as its over 4 miles away. We hop on our bicycle, and pedal four and a half miles to a Starbucks. We will expend approximately 260 calories. Great job!

We feel so good about ourselves, we order a Grande Caffe Mocha instead of our plain black coffee. It has 260 calories. Grab a muffin, a mint, or anything else, and if you accept the idea that calories matter, you are worse off than before.

What if we sat home and didn’t cycle? In that hour you would have expended 55 calories sitting on the couch knitting. Not exactly exercise, but if knitting keeps you from drinking that Grade Caffe Mocha, you are ahead of the game.

And that’s accepting the flawed idea of “calories in and calories out” used by so many of the same people that say “get off your fat arse and exercise”.

The truth is that we are more complex than machines. We don’t have gas tanks, and we don’t burn fuel. We digest food and metabolize it. In Loser, Biggest Loser we recounted Dr. Doug McGruff’s horror at seeing the TV show “The Biggest Loser” while on shift in his ER. The mistreatment of the contestants on the show, combined with the erroneous ideas promulgated by the sadistic “personal trainers”, is a prescription for failure.

Exercise conveys many benefits, but if you have to choose between adopting a better diet and exercise to lose weight, choose the diet. And the best diet we have found is the low carb diets, such as Protein Power, The New Atkins, or one of the other paleo diets now popular.

Exercise Doesn’t Shed Pounds?

Gary Taubes, the nationally acclaimed science writer, explains why exercise and weight loss are not physiologically linked:

The one thing that might be said about exercise with certainty is that it tends to makes us hungry. Maybe not immediately, but eventually. Burn more calories and the odds are very good that we’ll consume more as well. And this simple fact alone might explain both the scientific evidence and a nation’s worth of sorely disappointing anecdotal experience.

The New York magazine article is a good read, and includes Taubes’ signature style of including historical perspective to frame the issue. And he gets to the underlying philosophy behind the “calories in / calories out” theory of weight loss: the idea that the body is a thermodynamic black box that has to respond to the balance of calories taken in and calories expended.

But we are not gasoline engines. Taubes explains that the thermodynamic black box theory (TBBT) fails to take into account the role of fat tissue in our metabolism. Studies showed fat people maintaining or gaining weight while eating less than thin counterparts. But the thin people were more active. The correlation seemed to support the TBBT theory. But studies of overweight people who increased activity substantially, including a controlled study where Finnish researchers trained overweight men and women to run a marathon, showed that they maintained their weight.

Overweight people who have tried the “diet and exercise” remedy can commiserate with their Finnish brothers and sisters.

Taubes relates that our bodies have been shown to try and maintain certain levels of blood sugar, hormones, etc. We have evolved to try and counteract the entropy of our environment and gradual breakdown of our bodies. Our survival depends on it:

The key is that among the many things regulated in this homeostatic system—along with blood pressure and blood sugar, body temperature, respiration, etc.—is the amount of fat we carry. From this biological or homeostatic perspective, lean people are not those who have the willpower to exercise more and eat less. They are people whose bodies are programmed to send the calories they consume to the muscles to be burned rather than to the fat tissue to be stored—the Lance Armstrongs of the world. The rest of us tend to go the other way, shunting off calories to fat tissue, where they accumulate to excess. This shunting of calories toward fat cells to be stored or toward the muscles to be burned is a phenomenon known as fuel partitioning.

What is the mechanism for storing calories as fat? Insulin, working in concert with an enzyme, lipoprotein lipase (LPL), determines if energy should be burned or stored as fat.

Low carb dieters know that one effect of eating a low carb diet is to even out the insulin response. Those of us with insulin resistance also know that as we even out the insulin response, our cells become less resistant to the insulin in the bloodstream, and more of the glucose in our blood is used for muscular energy rather than stored as fat.

A low carb diet is more than a weight loss diet; it is a lifestyle choice that leads to more stable weight for a lifetime. This is possible because, unlike exercise, eating lower carbohydrates in your daily diet aids in the feeling of being satisfied with the amount you have eaten. When you aren’t hungry, its easier to not reach for that snack.