Tag Archives: energy balance equation

Does Diminished Work Activity Explain Our 50-Year Overweight Trend?

Daily work-related energy expenditure over the last half-century in the U.S. has decreased by over 100 calories.  This may well explain the increase in body weights we’ve seen, according to a 2011 article in PLoS ONE.

I sorta hate to open this can o’ worms, but it’s important.  As a population, are we fat because we eat too much or because we burn too few calories in physical activity?  Or is it a combination?  The correct answer may help us learn how to reverse the trend.

Methodology

Authors of the study at hand estimated the amount of energy (calories) necessary to perform various jobs, then noted changes in numbers of people employed in those jobs over time.  In the early 196os, for example, nearly half of U.S. jobs required at least moderate intensity physical activity, compared to less than 20% demanding that degree of energy now.  The authors note the dramatic shift from manufacturing to service-type jobs over the last 50 years.  Service jobs, like mine, often entail a lot of sitting and standing around. 

They chose to ignore how much energy we expend in exercise, figuring what we do in a 40-hour work week overwhelms the 1-2 hours of  exercise we may do.

Researchers’ Findings and Conclusions

They found that work-related daily energy expenditure has decreased by over 100 calories over the last half-century, which (in the authors’ view) would account for a significant portion of the increased body weight we’ve seen.  Since physically demanding jobs are unlikely to see a resurgence, the authors advocate physically active lifestyles away from workplace. 

Discussion

Surveys indicate that only one in four of us fulfill the federal physical activity guidelines: 150 minutes a week of moderate intensity activity or 75 minutes a week of vigorous intensity activity.  When activity is actually measured with an accelerometer, only one in 20 achieve that lofty goal.  We over-estimate how much we exercise, and under-estimate how much we eat.

(If you want to emulate a Paleolithic lifestyle, you should probably shoot for an hour of exercise daily, not 20 minutes as above.)

The researchers cite studies showing significantly increased average per capita calorie consumption in the U.S. over the last several decades.  Some experts estimate the caloric increase is in the range of 500 a day for adults; the authors here think that’s too high but don’t offer a specific alternative. Looking at one of their references (Hall et al), they must think the increase is closer to 200 calories a day, comparing 2005 to 1975.

Several studies suggest that average daily energy expenditure has not decreased in developed countries, at least from the 1980s to the present.   A strength of the current study at hand is that it spans about 50 years, up to 2008.

My sense is that both calorie consumption (too much) and physical activity (too little) contribute to our overweight problem that started 40 or 50 years ago.  Excessive consumption is the predominant factor.  To “exercise off”  the calories in a Snickers candy bar, you’d have to jog for an hour.  If you’re watching your weight, you’ll have more success if you just skip the Snickers.

In case you couldn’t tell,  I still believe in the “calories in/calories out” model of overweight and obesity, aka “the energy balance equation.”  At the same time, I believe certain foods  are more fattening than others: concentrated sugars and refined starches.

Steve Parker, M.D.

References:

Church, T.S., et al.  Trends over 5 decades in U.S. occupation-related physical activity and their associations with obesity.  PLoS ONE, 2011, 6(5): e19657.  doi: 10.1371/journal.pone.0019657  

Swinburn, B., et al.  Increased food energy supply is more than sufficient to explain the U.S. epidemic of obesityAmerican Journal of Clinical Nutrition, 2009 (90): 1,453-1,456.  

Hall, K.D., et al.  The progressive increase of food waste in America and its environmental impact.  PLoS ONE, 2009, 4(11): e7940.  doi: 10.1371/journal.pone.0007940

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The Holy Grail: Prevention of Weight Regain

Losing excess weight is easier than keeping it off.

Neither is exactly a walk in the park.

Prevention of weight regain is the most problematic area in the field of weight management.  You may have heard that “diets don’t work,” but they do.  Many different weight loss programs work short-term, if “work” is defined as loss of five, 10, or more pounds while you adhere to the program for several weeks or months.  The problem is that the lost pounds usually return.

Why?  You get bored with the diet, or your willpower flags, or the diet simply stops working, or the transition from weight loss to maintenance is unclear, or you just feel too bad to go on, or you lose your commitment, or you take a job as a taste tester for Baskin-Robbins Ice Cream, or whatever. 

Most diets ultimately fail in the long run because people go back to their old habits. 

Read on for the secret to prevention of weight regain.  They apply to a majority of weight-loss methods, although many programs ignore this problem because the cure is a hard pill to swallow. 

Moving Ahead

For purposes of further discussion, I will assume that you have already lost excess weight down to your goal and now we must focus on staying thereabouts from here on out.  Finally down to your goal!  A grand accomplishment!  You’ve got a new wardrobe, or the old clothes fit again.  You have more energy and feel younger.  Maybe you cured or improved some health problems.  Perhaps you’re getting more attention from the opposite sex (ooh la la!). 

Our species’ scientific name is Homo sapiens.  It is from the Latin sapere, which means “to be wise.”  Wisdom is the ability to make correct judgments and decisions.  Undoubtedly, your success at weight loss required correct judgments and decisions.  You are not done yet.  You will need sustained wisdom to avoid weight regain.

Be wise about this especially: you can never again eat all you want, whenever you want, over sustained periods of time.  

Now that you have reached your goal weight, you must restrain yourself on a daily basis.  Think about it.  You became overweight because you didn’t watch what you ate and didn’t exercise enough.  You can’t go back to your old ways.  Reject this advice, and you have a 100 percent chance of regaining your lost weight. 

Have you heard of the Energy Balance Equation?

Calorie Intake minus Calories Burned

         =  Change in Body Fat

You have been able to lose fat weight because you ate less energy (calories) than your body required for metabolism and physical activity.  Your body remedied the energy deficit by converting fat into energy.  A pound of fat contains 3,500 calories of energy.  If you lost a pound per week, your body on average converted 500 calories of fat daily into energy (7 days x 500 calories = 3,500 calories = 1 pound of fat). 

Now that you are at your goal weight and want to stay there, you need to add 500 calories per day back into the equation.  Add the calories by eating more food, exercising less, or a combination of the two. But if you add back more than 500, you will regain weight.

The true measure of a successful weight management program is not simply how much weight is lost, but whether the lost weight stays lost over the long run.  What distinguishes weight losers who keep the weight off from those who gain it back?  Two factors, mostly:

          1.  Restrained eating
          2.  Regular physical activity
.

“Successful losers” apply self-restraint on an almost daily basis, avoiding food that they know will lead to weight regain.  They limit how much they eat.  They consciously choose not to return to their old eating habits, despite urges to the contrary.  The other glaring difference is that, compared to regainers, the successful losers remain physically active.  They exercised while losing weight, and continue to exercise in the maintenance phase of their program.  This is true in at least eight out of 10 cases.  It’s clear that regular exercise is not always needed, but it dramatically increases your chances of long-term success. 

In a nutshell, my maintenance phase prescription for you is: Keep exercising, and eat a little more.  Keep exercising, and eat a little more.

Go out of your way to be physically active for 30 to 45 minutes on at least four days per week, if not all days.  Walking is fine.  The more you exercise, the more you can eat without getting fat again. 

At the end of your weight-loss phase and the beginning of the maintenance phase, it is surprisingly easy to start overeating.  Forewarned is forearmed.  Avoid this landmine any way you can.  It helps to continue monitoring food consumption and exercise on your food diary while eating an additional 200–500 calories per day.  Continue weighing daily.  Keep exercising.  After a month or two of this regimen, you’ll have an intuitive sense of what and how much you should be eating without regaining weight.  Then stop the daily log routine. 

Another option for transition to the maintenance phase: if you have been exercising regularly but loathe it, you could stop exercising and stay on your current calorie level diet.  In other words, don’t start eating more.  See what happens with your weight.  Perhaps you could later eat an extra 100 to 200 daily calories without gaining weight.  Continue recording your daily intake and weight for a couple months.  

Weigh yourself daily during the first two months of your maintenance-of-weight-loss phase. After that, weigh weekly.  Daily weights will remind you how hard you worked to achieve your goal.  When you look now at a brownie, candy bar, or piece of pie, you ask yourself, “Do I really want to walk an extra hour or jog an extra three miles today to burn off those calories?” If so, enjoy. Otherwise, forego the unneeded calories. 

Be aware that you might regain five or 10 pounds of fat now and then.  You probably will.  It’s not the end of the world.  It’s human nature.  You’re not a failure; you’re human.  

But draw the line and get back on your old weight-loss program for one or two months.  Analyze and learn from the episode.  Why did it happen?  Slipping back into your old ways? Slacking off on exercise?  Too many special occasion feasts?  Allowing junk food back into the house?  Learn which food item is your nemesis—the food that consistently torpedoes your resolve to eat right.  For example, I have two—candy, and sweet baked goods such as cookies and muffins.  If I just look at them I add a pound.  Remember an old ad campaign for a potato chip: “Betcha can’t eat just one!”?  Well, I can’t eat just one cookie.  So I don’t get started.  I might eat one if it’s the last one available.  Or I satisfy my sweet craving with fresh fruit or a diet soda.  Just as a recovering alcoholic can’t drink any alcohol, perhaps you should totally abstain from…?  You know your own personal gastronomic Achilles heel.  Or heels.  Experiment with various strategies for vanquishing your nemesis. 

It’s OK to overindulge in food infrequently (10–12 times per year), on special occasions such as birthdays, wedding anniversaries, holidays.  But you must counteract the extra calories by cutting down intake or by exercising more, either before or after the feast.  No big deal.

Click to read additional ideas on prevention of weight regain.

Steve Parker, M.D.

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