What Really Determines How Much You Weigh?

 by SJ McShane

You may have noticed in your weight-loss (or weight-gain) efforts that you body tends to stick around a certain weight range. So what gives? Here's what science tells us.

If you've ever hit a plateau in your weight-loss journey, you're not alone. The scale won't budge, and results stop. Whether you set out to lose or gain weight, at one point or another, your hard-earned results may have come to a screeching halt.

What gives? Fitness headlines chalk it up to the dreaded plateau and proceed to offer advice on how to break through it. But why do people hit this roadblock in the first place? A theory called body-weight set point just might be the reason plateaus hit with force, and why your body tends to sit comfortably around a certain number on the scale.

What's the Body-Weight Set Point Theory?

While there are conflicting opinions on whether "set points" actually exist, research suggests that the idea more or less holds true in practice. A 2010 review from F1000 Faculty Reviews cites eating disorder patients (specifically those with anorexia) as one example of the body's ability to bounce back to a certain weight.

And if you've noticed your own scale hovering around a particular weight range, it might not take much convincing. Simply put, the set point theory suggests that your body weight is regulated to a predetermined or preferred range.

"Think of it as a weight thermostat," says Eliza Kingsford, licensed psychotherapist and weight-loss expert. "If you set the thermostat in your home to 72 degrees, when gets too cold inside, the heat will kick on to keep things at 72 degrees. If it gets too hot inside, the air conditioner will kick on to also keep things at 72 degrees."

Your weight acts similarly. "Your set point will initiate different biological mechanisms to kick on so that your weight stays fairly stable, not letting you fluctuate too much in one direction or the other," Kingsford says. For some, this might be good news, but bad news for those unhappy with their weight. (Hold on, though, and keep reading!)

Read more: What Should I Weigh for My Age & Height?

What Determines Your Body's Set Point?

So what's going on here? From the looks of it, it all comes down to the brain. "The set point concept is based on what's called 'feedback regulation,' meaning our bodies receive feedback from the brain, and this feedback sets off a cascade of responses in order to regulate the mechanism we are receiving information about, in this case, our adiposity or body fatness," says Kingsford.

In other words, your set point is an extension of homeostasis — your body's way of keeping all your systems in balance. When your weight is "out of balance," your brain sends a message to the rest of the body to slow your metabolism and preserve the body's remaining weight, thus preventing further weight-loss. (It can also work similarly with weight/muscle gain, but only up to a certain point, as gaining weight is, unfortunately for many, much easier than losing.)

Although our body set weight is determined by a number of influences, including physiological (genetics and how each body system functions), cultural (the type of foods and eating habits you grew up with) and environmental (stress levels and availability of certain foods), there's much more science has yet to explain.

"There are few studies that can encompass every single one of these variables, so there isn't concrete evidence that this theory is the whole picture," says registered dietician Ryan Gebo. But it certainly provides a foundational framework for why you may have a hard time losing or gaining weight.

Is a Set Point the Same as Your “Happy Weight”?

You may have also heard reference recently to your "happy weight" — a number on the scale where you sit comfortably and confidently without having to perform two-a-day workouts or practice restrictive eating. A place where maintenance meets body confidence.

But does it differ from a set point? Sort of. "Your happy weight and your set-point are two different things — if only in your mind," says Kingsford. While your happy weight and set point might be the same number on the scale, your happy weight relies much more heavily on how you feel about that number. Alternatively, your happy weight may be higher or lower than your set point, if you're satisfied with the level of diet and exercise it takes to maintain that weight.

Regardless of your set point, your true happy weight is whatever weight you are when you're doing the following things Kingsford outlines:

  1. Making food choices that help you feel good emotionally and physically and don't leave you feeling shame or guilt after eating.
  2. Getting regular physical activity of some sort — ideally daily.
  3. Choosing forms of exercise that don't stem from punishment and compensation, but instead because it feels good to move your body.
  4. Maintaining your weight in a way that doesn't feel like a constant struggle or battle to keep yourself at that weight either physically or emotionally.

Read more: How to Find Your Happy Weight at Any Size

Are All Weight-Loss and Weight-Gain Efforts Doomed?

For those stuck in a rut, there is hope! Kingsford says it's absolutely possible for you to adjust your weight thermostat back down, but it's not a quick fix. "Your biology will work against you," she says. "But with consistency, this can be accomplished!"

If you commit to consistent behavioral changes you'll be able to adjust your thermostat so that it now supports lower body weight. Kingsford offers the following as examples of some of the things you can do to make sure you're adjusting your thermostat in a healthy way:

  1. Ensure that you're not inadvertently overeating (or undereating) by tracking your food intake for a period of time so that you can understand your caloric needs. (Try an app like MyPlate.) Use that as a baseline for future food intake that doesn't require obsessive monitoring.
  2. Increase your activity level (incrementally) either duration or intensity so that your metabolism starts to support a higher caloric burn. Find an activity that you really enjoy and look forward to.
  3. Modify your diet to reduce your consumption of processed foods that unnaturally stimulate the same biological responses that trigger overeating.
  4. Increase your consumption of nutrient-dense whole foods in order to regulate your insulin levels and kickstart your body's natural hunger and fullness cues.

Read more: Why Slow and Steady Wins the Weight-Loss Race


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