What’s the Best Diet to KEEP off that Summer Weight Loss?

Low Fat, Low Glycemic or Very Low Carbs?

It has been the gospel of the medical and health fitness community for decades, if not centuries,  that body weight maintenance is pretty simple: if you consume more calories than you expend you will gain weight; if you consume fewer calories than you expend, you will lose weight.  Calories in = Calories out +/- weight gain/loss.

Low fat diets have been encouraged by the USDA since the beginning of the food pyramid.   Low carbohydrate diets have been somewhat successful and increasingly trendy for the past few decades as well as consumers look for an edge.   Then there are ‘lunatic fringe’  extremely low carbohydrates diets like Atkins with extremely high fat content.

Keeping it off is the Biggest Challenge

Weight loss is one thing.   Overweight and obese folks have found success losing weight with these and many other approaches over the years.   Keeping the weight off, however, appears to be a <ahem> much larger battle.    Indeed, a  2010 report found that  only 1 out of every 6 people who has ever been overweight has reported long term weight reduction of more than 10%.

Wow.  

Fewer than 20% of anyone overweight who’s lost some weight can claim to have kept off as little as 10% of it in the long term. In other words, 80% of you who have lost weight gain most of it back …  eventually. 

That’s HORRIBLE! 

So, what researchers did was investigate the long term effectiveness of 3 dietary models in keeping the weight off after the once overweight study population lost the weight.   What they found, surprisingly, is that not all calories are quite the same when trying to keep the weight off. 

When a Calorie is NOT a Calorie

Three distinct types of diets were prescribed to those in the study:

• A typical USDA type low fat diet
  •  (60% carb; 20% fat; 20% protein)
• A low carbohydrate diet 
  • (40% carb; 40% fat; 20% protein);
  • with the further constraint of also being Low Glycemic;
• A very low carbohydrate diet
  • (10% carb; 60% fat; 30% protein)

Taking a look at three distinct dietary models, researchers from 7 institutions collaborated on a study showing that the type of calories consumed after weight loss, DOES INDEED matter in how well the weight is kept off.    The closely controlled study, conducted primarily in the Boston area regulated diet for an already overweight study population.  Then, for those individuals who were successful in losing weight, they further studied what type of diet is better for keeping the weight off.

In drawing their conclusions the researchers focused primarily on Energy Expenditure.   The theory behind studying energy expenditure in analyzing dietary effectiveness goes something like this:

• ‘calories’ are commonly substituted for  ‘Calories’ which are commonly substituted for ‘Kilocalories’
  • 1 Kilocalorie is amount of energy required to raise 1g. of water 1 degree Centigrade;
  • calories are energy physics, pure and plain
• When Energy Expenditure is reduced in the human body,  the calories in = calories out equation becomes imbalanced in a negative way with weight gain
• If a particular diet of identical caloric value was effective in either increasing Energy Expenditure, or reducing it less than other diets, that type of calorie content would matter in long term weight loss

In the end, it was indeed about finding a diet model that reduced Energy Expenditure less.   Energy Expenditure always went down with weight loss, but was reduced less in some diets.

Testing Low Fat, Low Glycemic and Very Low Carb Diets

If you’re curious about the study, you can read the entire Journal of the American Medical Association article here.     I’ll warn you it’s a lot of PhD researcher geek speak, but as far as controlled studies are concerned, you’d be hard pressed to find a scientific study going to greater lengths to manage all of the variables that might taint or otherwise sway outcomes.

It’s an extremely complex problem to account for:

• Age
• Gender
• Body composition
• Motivation to adhere to diet
• Hormone changes associated with glucose levels following a meal
• Psychologically sustainable food content, and
• Activity levels

Conclusions

While Resting Energy Expenditure and Total Energy Expenditure were primary outcome metrics,  hormone levels and metabolic syndrome components were also observed.  The team concluded that decreases in Energy Expenditure were “greatest with the low-fat diet, intermediate with the low–glycemic index diet, and least with the very low-carbohydrate diet,” suggesting that …

… the best way to keep the weight off would be a very low carbohydrate diet.

Additionally, the likeliest way to regain the weight was to maintain a low fat diet.  

Indeed, the two diets that attempt to “attenuate the increase in blood glucose levels”  were low GI and Very Low Carbohydrate.  They were  more effective in keeping Energy Expenditure reductions in check after a meal.

So, Very Low Carbs are Best then?

Well, not quite, because there’s a catch.   With diets there always seems to be a catch.

The study also recognized several deleterious effects of the very low fat diet:

1. Significantly wayward cortisol (stress hormone) levels; and
2. Alarming C-Reactive Protein levels widely recognized to increase the risk of heart disease

As a result, while apparently most beneficial in keeping the weight off, the adverse effects of the very low carbohydrate diet could not be recommended over the low glycemic index course.

It is fair to say that NOT all calories ARE EQUAL when in the context of long term weight loss. 

What to do then?

While interesting and insightful, this certainly isn’t the final word in sustained weight loss.

For while the methods and madness employed in the study had many strengths, the authors acknowledged weaknesses in the study as well:

1. The study was relatively short, covering just a few years.
2. The study only included individuals who were able to succeed with their initial weight loss efforts within a 7 month period which may be atypical.
3. The very low carb diet was assembled with food sources that likely were not sustainable over time.   And last, but not least is the fact that extending the study’s findings into a longer term, more natural environment of self selected foods could not (and may never) be accomplished.

 My personal conclusion on this is that science has a long way to go to identify the best diet for any population, including those who seek to keep lost weight off.

Even then, genetics, motivation and psychological factors may have an overriding and far greater effect at the individual level.

My suggestion?  Duh.  Just exercise more!

Be active and never let a day go by without moving vigorously in some way for 60 minutes.  

Not only will in balance the calories in = calories out equation, but you’ll gain all the other benefits of exercise in the process!