Fwd: Posts from The Healthy Skeptic for 08/12/2011

[Guest guest]

Excelent discussion about the complex causes of obesity.

Includes a great graphic depicting the interplay of all the identified

variables.

Osowski MS, RD, LD

Registered Dietitian

Posts from The Healthy Skeptic for 08/12/2011

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There is no single cause of (or treatment for) obesity

Aug 12, 2011 08:28 am | Kresser

One of the most hotly debated subjects over the past few years has been the

cause of the obesity epidemic, and along with that, the best strategy for weight

loss.

Some folks (Atkins, Taubes, Eades, etc.) believe that carbohydrates are to

blame. Others (Ornish, , Esselstyn, Fuhrman, etc.) believe that fat is

the problem. More recently, researchers like Seth and Stephan Guyenet

and clinicians like Dr. Sharma have raised awareness of another hypothesis,

called the food reward theory, which holds that the consumption of highly

palatable foods leads to overeating and weight gain. And Jaminet and others

have argued that micronutrient deficiencies, toxins and infections may play a

significant role in the obesity epidemic.

Here’s what I think: the most accurate answer to “why do people get fat?â€

and “what’s the most effective weight loss strategy?†is: “it

depends.â€

Separating cause from mechanism and effect

One of the biggest mistakes often made in this debate is the confounding of

cause, mechanism and effect. A classic example is the assumption that if

reducing carbohydrate or fat intake leads to weight loss, then the original

weight gain must have been caused by excess carbohydrate or fat consumption.

While it’s tempting to make such an assumption, the logic is faulty. It’s

kind of like saying “Advil cures headaches. Therefore, headaches must be

caused by Advil deficiency.â€

Let’s look at some definitions.

Cause: something that brings about an effect or a result

Mechanism: the fundamental processes involved in or responsible for an action,

reaction, or other natural phenomenon

Effect: an outward sign

Obesity is an effect. Insulin resistance, leptin resistance, lipotoxicity,

disruption of the mesolimbic dopamine reward pathway and inflammation of the

hypothalamus are presumed mechanisms. Excess consumption of carbohydrates, fat,

highly palatable food and food toxins (wheat, seed oils, liquid fructose, etc.),

exposure to environmental toxins (chemicals), stress, infections, etc. are

presumed causes.

Say we do a study on obese people and we observe that they eat a lot of

carbohydrates and are insulin and leptin resistance. It’s easy to assume that

the chain of causality worked like this: normal weight person eats

high-carbohydrate diet, becomes insulin and leptin resistant, and then becomes

obese.

But again, this is faulty logic. There’s no proof that A (high carbohydrate

intake) was what led to B (insulin and leptin resistance) was what led to C

(obesity).

In fact, we could disprove that theory simply by observing another individual or

group that eats a very high carbohydrate diet, but does not develop insulin or

leptin resistance and obesity. Guess what? Such individuals and groups most

certainly exist. There goes that theory.

Likewise, we could also disprove this theory by observing people that are

insulin and leptin resistant, but don’t become obese. Such people do exist,

and I’ve written about them in my series on diabesity here.

A more rigorous approach

How have we developed our theories on obesity and weight regulation? It seems to

me they come from a blend of personal experience, belief and facts. And I think

it’s time to become more rigorous about keeping them separate. Here’s an

example of what I mean:

Personal experience: I lose weight on an low-carb diet, therefore low-carb diets

must be best for weight loss.

Belief: carbohydrates are responsible for the obesity epidemic, via their

effects on insulin.

Fact: many cultures around the world eat high-carbohydrate diets and are

exceptionally lean.

Those who’ve lost a lot of weight on a low-carb diet have a tendency to become

convinced that their wife, friends, family, plumber and everyone else will also

lose weight following the same diet.

From this personal experience, a belief is formed. And once we believe in

something, we have a remarkable ability to filter out any evidence that might

contradict that belief.

This is especially true if our reputation or financial livelihood is tied to

said belief. As Upton Sinclair famously said:

It’s difficult to get a man to understand something when his salary is

dependent upon him not understanding it.

When a belief like “carbs cause obesity†is shared between enough

individuals, it becomes a meme. Once that happens, it is accepted by most as

fact – regardless of whether it has any scientific basis. Hence we had the

idea for decades that eating fat makes you fat, and now the more recent idea

that eating carbs makes you fat.

There’s no single cause (or treatment) of obesity

Perhaps one of the reasons it’s so easy to confuse cause, mechanism and effect

and personal experience, belief and fact is that obesity is an incredibly

complex disease. Just how complex is it?

Click on the Obesity Systems Influence Diagram below to find out.

Click image for larger version

Wow. That should give you a rough idea of how many variables are potentially

involved in weight regulation. Now you know why it has been such a challenge to

come up with a single, unified theory of obesity.

That said, of all of the hypotheses advanced to explain the mechanisms behind

obesity, I think the food reward theory is the most inclusive.

However, as even its proponents would agree, it doesn’t tell the whole story

because there are people and groups that eat large amounts of highly palatable

foods that do not become obese.

My opinion is that the modern lifestyle (i.e. food and environmental toxins,

stress, poor gut health, infections, micronutrient deficiencies, sleep

deprivation, etc.) interfere with hypothalamic hormonal regulation, dopamine

signaling, leptin and insulin sensitivity at the cellular level, glucose

metabolism and a range of other mechanisms that lead to obesity.

This is consistent with the observation that obesity is extremely rare or

nonexistent in traditional cultures that do not consume modern foods and do not

live a “modern†lifestyle.

But even this theory is incomplete, because there are people fully exposed to

the modern lifestyle that do not become overweight or obese. This suggests that

genetics, and perhaps other undiscovered factors, also play a role.

We’re not robots

Humans are not robots. We’re living, breathing, dynamic organisms influenced

by varying genetics and environmental conditions.

Anthropological evidence combined with modern research has helped us to reveal

the basic template of a species-appropriate diet. However, it has also shown us

that humans can thrive on a wide variety of macronutrient ratios and foods

within that basic template.

This is not a belief. It’s a fact, supported by the evidence as a whole.

Ignoring the evidence doesn’t make it go away. Believing passionately in

something doesn’t make it true. Experiencing something personally doesn’t

make it fact for everybody else.

19th century philosopher Peirce said:

The state of belief is a calm and satisfactory state which we do not wish to

avoid, or to change to a belief in anything else.

And Tolstoy said:

I know that most men, including those at ease with problems of the greatest

complexity, can seldom accept even the simplest and most obvious truth if it be

such as would oblige them to admit the falsity of conclusions which they have

delighted in explaining to colleagues, which they have proudly taught to others,

and which they have woven, thread by thread, into the fabric of their lives.

Recognizing this basic human trait, philosopher of science Karl Popper advised

every researcher to earnestly try to discredit their own hypotheses.

That is no easy task, and it asks a lot of us. Yet intellectual rigor, emotional

maturity and personal integrity are characterized by the capacity to question

our own beliefs, no matter how deeply cherished they are or how much is at

stake.

I sometimes wonder why we’re all so sure of ourselves. It helps me to remember

that at every point in history scientists (and the general public) were

convinced they had the right answers. At one time the world was flat, the earth

was the center of the solar system and disease was caused by foul humors and

could be cured by bloodletting.

Nowadays we look back on those fallacies with a smirk. But are we so arrogant to

assume that our great-grandchildren won’t do the same?

The truth is, there’s far more we don’t know than we do know.

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