What Happens To Your Body When You Start A New Diet?

Diet is often touted as the key to feeling fitter, living longer, and even looking better (though that last point is highly subjective). In fact, the Centers for Disease Control and Prevention found that 17% of American adults were on some kind of special diet between 2015 and 2018, a higher percentage than just a decade earlier.

From the keto diet to intermittent fasting to veganism, the purported benefits — and drawbacks — may vary between plans, but most people seem to adopt new diets for the same reasons: to boost health, and, in some cases, lose weight.

But unfortunately, these benefits aren't always noticeable right away, and the hard work and perseverance required can be a barrier for many — just ask the 79% of dieters who admit they're unlikely to stay committed to their new eating habits (via Newsweek). However, maintaining realistic expectations and understanding how a diet affects the body can determine whether or not someone actually sticks to their program. Here's what might happen to your body once you change your eating habits and how long it can take to see results.

Some effects kick in right away, while others require patience

Not all health benefits associated with a balanced diet can be easily detected, but that doesn't mean your body isn't changing. Some health perks quietly kick in almost immediately after you've modified how you eat. Dr. Terry Wahls, a board-certified internal medicine physician, told MindBodyGreen that healthy foods can start to repair your gut within just 20 minutes, and replacing inflammation triggers (like sugar and simple carbs) with their non-inflammatory counterparts (think veggies and whole grains) can improve brain function within a few hours.

However, it can still take time for the body to truly transform. "The benefits evolve over months, sometimes years," Dr. Mark D. Lurie, cardiology director at Torrance Memorial Medical Center, explained to U.S. News & World Report. "Physiologic changes will start quickly, but the true effect takes time." This can vary depending on your diet and health goals. For example, a 2011 study published in Diabetologia suggested that type 2 diabetes could be reversed within eight weeks of adopting a low-calorie diet. For heart-healthy diets, WebMD notes it can take between three weeks and three months to see results in clinical lab work.

As for losing weight, no two bodies are the same, and not all diets are fail-safe. The rule of thumb, says Cleveland Clinic, is to consume fewer calories than your body needs. Your system will then use stored fat for fuel, expelling it through your sweat, urine, and CO2.

Starting a new diet isn't always easy on your body

A new, healthier diet may boost your gut, brain power, heart health, and other bodily functions, but that doesn't mean you'll feel better right away. This comes as no surprise to almost anyone who's ever dieted — discomfort, at least initially, seems to be just part of the package deal. "The number one thing I always hear about transitioning to a healthier diet is bloating, gas, and having an upset stomach," Jaclyn London, a registered dietitian, shared with Good Housekeeping.

Another common struggle: food cravings. Ditching sugar-laden and high-calorie foods at the start of a new diet can make those foods seem even more irresistible than usual. "If you have a cookie every day after school, just walking into the house cues you to have a cookie," Dr. Marcia Pelchat, a food researcher at the Monell Chemical Senses Center, explained to WebMD. "If you don't get that cookie right away, your mind obsesses about it and turns it into a craving." Then, according to a 2018 study published in Appetite, you may suffer withdrawal symptoms including irritability and fatigue.

Not all dieting side effects are normal, though. A highly restrictive diet that deprives the body of essential nutrients or that triggers rapid weight loss can lead to dangerous consequences. If your body reacts with cramps and aches, dizziness, bowel issues, dry mouth, or hair loss, take it as a sign that your diet is too restrictive (per NHS).