Human Limits

A colleague who wants to lose some weight sent me an e-mail asking about the “Wheat Belly” diet which advocates cutting wheat based products and foods from your diet.  A book based on this concept is a best seller and among other things there is discussion in the book about how “addictive” wheat based products are and some potentially bad biological effects of high yield varieties that have emerged through selective breeding over the last 50-100 years.  From what I can tell, this is just the latest iteration of the “low carb” approach to weight loss and dieting that has had a number of incarnations over the last 50 or more years.  So, what did I tell my friend?

 

1)  Low Carb Diets Reduce Variety

There is pretty good evidence that just restricting food variety reduces the amount we eat.  Get rid of wheat based products and you restrict variety a lot.   Here is a link to an animal study that makes this point:

 

“Thus, the present results suggest that limiting dietary variety, regardless of palatability, may be a useful strategy for weight loss in overweight and obese individuals by reducing caloric intake within individual meals.”

 

2)  Carbohydrate Restriction & “Water Weight”

The pictures below are two photos taken a few days apart of Olympic 1500m swim champion Grant Hackett.  On the left is a shot when he was tapered and after he had carbo loaded for a 10k open water swim (the swimming equivalent of a 26 mile marathon).  The photo on the right is a few days later when he was back to his normal training.  Along similar lines, it has been known for years that low carb diets lead to rapid weight loss because water is stored along with carbohydrate in the body.  When the carbs are depleted the water goes with them.   A study from the 1990s tracked this carefully over a few days of a very low calorie diet and showed a 4.3 kg (9 lb) weight loss almost entirely from changes in body water.  A lot of the appeal of low-carb diets is this early and impressive weight loss.  Don’t be fooled into thinking it is fat loss.

 

 

3)  Feeling Full Helps

Dietary fat and protein probably make most people feel full for longer.  The biology is complex and relates to how fast food leaves various parts of your digestive tract and a whole bunch of hormonal signals related to what makes us hungry and what makes us feel full.   So, this is perhaps another reason that low carb diets seem to work.   However, there is concern that low carb but high fat and protein diets work but are not optimal to reduce or control things like cholesterol.  This too is a complex topic with a lot of individual variability.  But feeling full for longer is good if you want to lose weight.

 

4)  The Brain & Food Addiction

The way the brains of people who are obese or prone to overeat are stimulated by food or images of food is different.  Does this mean they have a food addiction?  Who knows, but the summary below does give us some hints about what the issues are and what might be done to address them.

 

“Prefrontal cortex areas linked to cognitive evaluation processes, such as evaluation of rewarding stimuli, as well as explicit memory regions, appear most consistently activated in response to images of food in those who are obese. Conversely, a reduced activation in brain regions associated with cognitive control and interoceptive awareness of sensations in the body might indicate a weakened control system, combined with hypo-sensitivity to satiety and discomfort signals after eating in those who are prone to overeat.”

 

Is this innate?  Or does it happen over time.  Is it biology or environment?  My guess is that is probably both and that the brain can be rewired over time and with some effort.  Self-control related to both diet and exercise seems to be the key for long term successful “losers”:

 

“These findings suggest that weight loss maintenance efforts can be improved by addressing challenges such as long-term self-monitoring and problem-solving skills, and that maintenance success might depend on how people think as much as what they do.”

 

What is interesting is that both the brain imaging studies and the behavioral studies both cite issues related to body perceptions and self-monitoring.  Perhaps it is more than just will power and there is a “skill” and focus element to weight loss like most other things that are difficult to do.

 

5)  Exercise & Physical Activity

Most of us don’t have the time, energy or motivation to train like an elite athlete and be a in a position to essentially eat all day long.   However, there is some evidence that if we exercise a lot we might sit around more during the rest of the day and lose some of both the energy expenditure benefits and health benefits of exercising.   So a key thing to remember is to both exercise and also build more low grade physical activity into your day.

 

Summary

Despite wave after wave of claims related to low carb diets, at some level if you have seen one you have seen them all.  They clearly “work” at generating rapid weight loss, reducing dietary choice and they probably help people feel a bit fuller.  However, the key to successful long term weight loss appears to be related to developing the skills and behavioral strategies needed to effect long term changes in diet, exercise and overall physical activity.   What is interesting about my colleague is that he is highly successful, self-disciplined, and focused in many areas of his life.  He is also seen as a problem solver by many co-workers.  So, he has the general skill set needed to be a successful “loser”, and my bet is that he will be once he consistently applies these skills to his exercise and weight loss goals.

 

This entry was posted on Thursday, July 11th, 2013 at 5:14 am and is filed under Current Events, Research and Health. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.