• After I overeat, how long before I gain weight?

    Several athletes (and non-athletes) I know have mentioned that it seems they have a two-week rule. That is, they seem to be able to overeat for a period of time and then after roughly two weeks – boom! The scale says weight gain.

    The opposite seems to be true for these people as well. That is, when they begin the New Year’s resolutions of weight loss it take two weeks of vigilance before the scale shows a stable weight loss.

    What is going on?

    There are many factors that influence whether you gain weight or lose weight. Let’s begin with a single bout of overeating. You and your friend have weighed in prior to your meal. Your friend enjoys few things in life more than celery. S/he eats a pound of celery. You know that life is too short and you’re going to enjoy the trip. Furthermore, you love sweet chocolate. Your buddy has just consumed 64 calories and you enjoyed around 2288 calories.

    You both jump on the scale shortly after your “meal” – and what happens? Assuming you consumed nothing else and didn’t void before weigh in, you both gain one pound.

    But what happens in the next few days? Will you gain weight and will your friend lose weight?

    It is a complex answer that involves digestion, metabolism and energy expenditure. This energy output includes your lifestyle (deliver packages all day or sit in front of a computer) and your exercise routine or training plan (training for triathlon, mountain biking, cycling events, etc.). In the big scheme, if you eat more calories over the course of time than you burn, you will gain weight.

    Here’s what we know:

    -  Generally, we do not increase the number of fat cells in our bodies after the onset of puberty. The exceptions are if you gain a significant amount of weight or if you’ve had liposuction performed.

    -  A lean adult has around 40 billion fat cells and an obese person has some two to three times that value.

    -  For the most part, the fat cells you have ones you have just get bigger when you consume too many calories. For people that are obese, the fat cells look as though they are going to burst when examined under a microscope. These huge cells send signals to other immature cells and tell them to begin dividing.

    -  Mayo Clinic researchers designed an experiment in the 1980s that measured digestion time in 21 healthy people. Total transit time, from mouth to elimination, averaged 53 hours.

    -  Whether calories are burned or turned into fat will depend on your metabolic rate, your lifestyle and your exercise patterns over a period of time. The body likes consistency.

    -  Sustained weight gain (or loss) takes time to stabilize. Gaining one or two pounds after eating a big meal may not be sustained weight gain. Also, as all athletes know, losing one or two pounds after a workout may not be sustainable and is often a good deal of body fluid (sweat).


    I couldn’t find an exact answer to the question of, “How long before I gain weight after overeating?” because of the complexity of the seemingly simple story problem. I suspect overeating one day (pick any holiday) won’t show up on the scale as a long-term weight gain until around three or more days after the indulgence (assuming you continue to eat and exercise at “normal” rates after the indulgence).

    The trouble isn’t one day of indulgence. The trouble is telling yourself, “Oh well, I blew it yesterday, I might as well overeat (or drink) today too. I’ll start my “diet” on Monday.”

    If this continues week after week, you’ll have a big project come New Years Day or the first time you put on shorts next spring…


    Reference list available on request.

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