Can you Become Obese by Eating Just an Extra Bite of Food per Day?

Jane Brody (veteran food columnist for the New York Times) recently reported, “According to researchers is easy to gain weight unwittingly from a very small imbalance in the number of calories consumed over calories used.” Brody continues, “Just 10 extra calories a day is all it takes to raise the body weight of the average person by 20-pounds in 30 years, the authors wrote.”

What do you think Ms. Brody meant in the preceding statement?

a) You can gain weight endlessly with as little as 10 extra calories per day.

b) As long as you continually ratchet-up your average energy intake, by as little as 10 calories (above your energy needs), you will gain weight slowly but steadily.

Although you might think it's as clear as mud, both (a) and (b) arguably mean the same thing. The key word in (a) is “extra,” meaning “above your energy needs.” However (b) makes it much clearer that a steadily rising (average) energy intake precedes a steadily rising body weight.

I'm not sure if Ms. Brody understood the researchers' point or not. However, if she did, she certainly did not ensure that her readers would understand it.

We're talking about a research paper by Kevin Hall[i] that set off a slew of erroneous news coverage regarding calories and weight gain/loss. It’s a complicated topic, and few outside the research community familiar with it actually know the area of literature well enough to discuss it off the cuff. The topic can’t easily be reduced to short comments or sound-bites without leaving out lots of caveats, and important or seemingly contradictory details. This is my second blog addressing some of the erroneous reporting.

According to the authors, if you started eating 10 calories per day, above your current average (and stayed at that level), you would only see 1-pound of weight gain—not 20-pounds! This is why the "ratcheting up" point is key.

“A simple approximate rule of thumb… every permanent change of energy intake of 100 kj per day will lead to an eventual weight change of about 1 kg [equivalently, 10-calories per day per pound].”   --Hall K., et al.[i]

A critical related point that Hall made is that some researchers have failed to take into account that there is an increase in maintenance-energy-needs as weight is gained, which means that weight-gain will cease (plateau; stabilize) when increased maintenance-energy-needs match the average intake consumed.

Here's one of those caveats: Technically, Hall doesn't consider weight stabilized until substrate utilization matches body composition. That caveat/side thread however, has little practical significance to the main point, and will require a blog of it's own! 

Hall’s concern is that when researchers fail to take the plateau into account, their projections erroneously give the impression that a small calorie excess leads to ongoing weight gain. Or conversely, that a small calorie deficit will lead to erroneous weight loss projections for public health policy efforts, such as a soda or junk food tax.

The section of Hall’s paper that discussed this specific thread was titled, “Modeling average weight change in a population.” Clearly care needs to be taken when attempting to translate data from population modeling to individuals. Hall uses a graphic to make a couple of the key concepts more obvious. Here's my version of his chart:

[Enlarge Chart]

Energy Imbalance Gap: Literally it's the "gap" between the Energy Intake and Energy Expenditure lines. It's a small gap. Hall describes it as the simulated linear increase of average energy intake and energy expenditure underlying the observed increase in the average bodyweight (in the US population) between 1975 and 2005.

To put it in laymen terms what we see is: the more people eat the more they gain, and the more they gain the more they eat. 

Note: Energy expenditure and Maintenance-energy-needs are synonymous meaning the total number of calories required to maintain current body weight (consisting of: 1) resting metabolic rate, 2) the thermic effect of food, and 3) activity of daily living/exercise).[ii]

Maintenance Energy Gap: the difference between the energy intake required to maintain current body weight compared with a previous body weight. In this case the average body weight of the US population increased from ~157-pounds to ~178-pounds (a gain of ~21-pounds) over 30 years. The difference in maintenance-energy-needs between those two weights is ~229-calories per day.

If the graph represented an individual, they could theoretically gradually return to their 1975 body weight by permanently reducing their maintenance-energy-intake by the 229-calories per day. Technically they could also increase their average energy expenditure to balance-off all or part of the 229-calories per day, and also return to their 1975 weight. 

While these are generalizations, that fact remains that body weight is a numbers game. It's true that individuals will vary plus or minus 10% in resting metabolic rate (RMR), even of the same body weight/composition, age and gender. That variance seems to be mainly the genetic hand they were dealt. But once your RMR is established, you know what you are working with. Remember it's a bell curve and you are just as likely to fall on the upper half of it as the lower half.

Takeaway #1: Maintenance-energy-needs rise along with (as a result of) weight gain. So steadily rising (average) energy intake always precedes a steadily rising body weight. (The only exception to this would be when weight-gain is preceded by a drop in activity expenditure that isn’t balanced off by a matching drop in energy intake.) The reverse of this rule is also true: maintenance energy needs decrease with (as a result of) weight loss. Plateaus, during weight gain or loss, indicate that average energy intake and average energy expenditure are equal (balance each other out).

Takeaway #2: Reversing the weight gain trend--for individuals--could be as easy as identifying enough permanent tradeoffs to cut out the Maintenance Energy Gap. For instance if you usually drink coffee with cream and sugar, and you cut out the cream, sugar, or both, you would save 16-calories per teaspoon of sugar, and 20-calories per tablespoon of half-n-half. The key is to identify tradeoffs that work for you, otherwise they won't last. You can also see why portion sizes and second helpings are important (and add up or down!).

In a future blog I will tackle how body composition (ratio of lean body mass and fat mass) affects weight gain or loss. 

Best,
-Dorene

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Related articles:
Set-Point Theory: Fact or Fiction? 
Set-Point Theory: a few more thoughts 
 

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[i] Hall, KD, et al. Quantification of the effect of energy imbalance on body weight. Lancet 2011;378:826-37.

[ii] Weinsier RL, et al. Predicted effects of small decreases in energy expenditure on weight gain in adult women. International Journal of Obesity 1993;17:693-700.