It’s a disturbing statistic.

Two thirds of Americans are overweight or obese according to National Health and Nutrition Examination Survey, 2009–2010.

Which means chances are you know someone personally who may have struggled with what’s known as “yo-yo dieting.”

That someone might even be you.

Because it affects so many people, today I’m going to take a look at what causes yo-yo dieting and whether or not it’s harmful to your health.

The actual term “yo-yo dieting” was coined by American scientist and renowned obesity expert Kelly David Brownell in the 1980s. It’s also known as the “yo-yo effect” and “weight cycling.”

The definition of yo-yo dieting is “repeated losses and regains of body weight.”

Here are the basic steps of how it occurs:

Step 1: You go on a low calorie diet of say 1,000 calories a day.
Step 2: Your body then goes into what’s called famine mode. Famine mode is when your body thinks it’s starving so it adjusts by slowing down your metabolism. It conserves fat and begins to burn muscle instead (which means you’ll burn fewer calories and lose less weight.)
Step 3: After a while 1,000 calories per day becomes more difficult to maintain. Hunger, fatigue and even depression may occur.
Step 4: You go back to your old eating habits. Anything over your 1,000 calorie a day intake results in you gaining weight.
Step 5: Within months you are right back where you started (or possibly even heavier) so you go back to step one and start all over again.

Can you relate even a little bit to the above?

There’s a good chance you can as it’s estimated that, at any given time, approximately 108 million Americans are trying to lose weight. What’s more, the typical dieter attempts to lose weight four times each year.

Recently the world did receive good news when it comes to yo-yo dieting.

For the longest time, it was thought that yo-yo dieting actually damaged your metabolism. Meaning that with each successive yo-yo dieting cycle, it made it more difficult for you to lose weight.

A 2013 study published in the journal Metabolism found yo-yo dieting does not damage metabolism.

Having said that, yo-yo dieting can definitely be detrimental to your health. I’ve put together five reasons you should avoid yo-yo dieting at all costs. Yo-yo dieting…

1. Increases your stress hormone – When you go on a low calorie diet, your body emits more of the stress hormone cortisol. In an article published on the Psychology Today website, athlete and author Christopher Bergland calls cortisol “public enemy number 1.” He writes that “Scientists have known for years that elevated cortisol levels: interfere with learning and memory, lower immune function and bone density, increase weight gain, blood pressure, cholesterol, heart disease… The list goes on and on.” Clinical studies done by Yale University (and many other universities) found that bringing cortisol levels down can reduce body-fat levels, control blood pressure, improve insulin sensitivity, balance blood sugar levels, and control appetite.

2. Boosts up the level of other hormones – Integrative medicine physician Andrea Pennington, MD, says that “Repeated crash dieting increases metabolic hormones, such as insulin, and elevates levels of sex hormones, including estrogen. These changes cause you to start putting on weight around your middle, which research has linked to insulin resistance, diabetes, high blood pressure, and heart disease.”

3. Can play havoc with your confidence – If added stress wasn’t enough, yo-yo dieting can also give your confidence a severe beating. New York City dietician Keri Gans, RD, says, “The more times you go through the gain-lose-gain cycle, the less convinced you become that you can break free from the constant ups and downs. No one wants to diet forever; it’s hard work.”

4. Could damage your heart – Women who weight-cycle five times or more during their lifetime may be damaging their hearts in the process according to a study published in Clinical Cardiology.

5. It could damage your immune system – Cornelia Ulrich, M.D., of the Fred Hutchinson Cancer Research Center in Seattle, did a study that found that women who repeatedly lost and gained weight had lower immune function, particularly lower counts of natural killer cells. “These cells are important for fending off infections and are also vital in fighting the early stages of cancer,” Ulrich says. Women who had yo-yo dieted more than five times had a reduction by one third of their natural killer-cell activity.

So what’s the answer?

With being overweight so hazardous to one’s health, if you do have some extra pounds the answer is not to throw up your hands and say “I give up.”

Regular exercise is key. As is what you eat of course. For years we’ve been told that “diets don’t work.” It’s true, they don’t. While you may lose weight, chances are you’ll gain it all back (and possibly more) once you revert back to your old way of eating.

The key is not to diet, but to change your day to day eating habits for life. Because here’s the thing, it’s often not how much someone eats, but what they eat.

Education is the key. You must learn to eat healthy in a way that is sustainable for life. This means taking a balanced macronutrient (the three macronutrients are fat, protein and carbohydrates) approach to what you eat so that you can once and for all make yo-yo dieting a thing of the past.