What Happens To Your Body When You Lose Weight?

Losing weight, when achieved through sustainable lifestyle changes, can improve many markers of health, including blood pressure, mobility, and energy. But to achieve these benefits, it's important to avoid quick fixes and implement weight management efforts that can be maintained for years to come.

To help you reach your weight loss goal, we asked registered dietitians for their best tips. We also had them explain what actually happens in your body when you lose weight—because we can all use some extra motivation to stay on track.

What Is Weight Loss?

Weight loss is a complex process influenced by a number of factors, including genetics, diet, and exercise. A reduction in body weight is typically achieved through a combination of dietary changes, physical activity, and lifestyle modifications. When the number of calories burned exceeds the number consumed, a calorie deficit is created, and stored energy is used to meet energy needs, resulting in decreased body weight.

"When you lose weight, your body uses stored fat for energy, and hormonal changes occur," says Mindy Roth, MS, RDN, a registered dietitian and owner of Mindy Roth Nutrition & Nourish Your Lifestyle Revolution.

Fat cells, which are present under the skin and on top of muscles, shrink as you lose fat. But, if you aren't eating enough to meet your energy needs, your body will also turn glycogen reserves in your muscles into energy. As a result, some muscle mass may accompany fat loss.

Why Losing Weight Can Be a Challenge

One reason weight loss may be so challenging is that the drive to eat is increased through hormonal changes. When you lose weight, changes in hunger and fullness hormones occur. Fat cells produce leptin, the hormone that sends the message to your brain that you have eaten and are full. But when fat cells shrink, less leptin is produced and you may not feel as full. Consequently, your stomach produces more ghrelin, or your hunger hormone, which tells the brain your body is ready to refuel.

"When your body senses weight loss, it's going to fight against it," says Miranda Galati, MHSc, RD, a registered dietitian and owner of Real Life Nutritionist. "All your body knows is that you're losing protective fat and muscle, so it's going to try to preserve it by reducing your energy needs and increasing your drive to eat."

Weight loss may also result in a slower metabolism, as the body interprets decreased calorie intake as a sign of distress. It works to shunt calories to the most important organs like your brain, heart and lungs, to keep you alive. It also stores fat to preserve for future energy in case food is not available.

Benefits of Losing Weight

Losing weight, when done in a healthy and sustainable way, can result in a number of benefits. These include improved metabolic health, reduced risk of chronic disease, enhanced mobility, and increased energy levels. Here's more on how you may benefit from weight loss.

Improves Metabolic Health

Metabolic health is taking a look at how the body is functioning internally and preventing a cluster of conditions called metabolic syndrome. In order to be diagnosed with metabolic syndrome, you need have to three out of the five conditions that include high blood pressure, high blood sugar, high triglycerides, low HDL or good cholesterol, and high waist circumference.

Lifestyle changes and weight loss may delay or prevent the development of metabolic syndrome. What's more, having good metabolic health means that your body is able to efficiently process food and nutrients that allow your blood sugar, blood pressure, cholesterol, and body weight to stay in a healthy range.

Increasing your metabolism, or resting metabolic rate, can also be a benefit of weight loss and help with weight maintenance. Going on a strict diet and decreasing calories too quickly can result in a slower metabolism. To prevent this, ensure that the calories you eat in a day match your resting metabolic rate. Your age, sex, and activity level can help determine your resting metabolic rate and how many calories are right for you.

Reduces Risk of Chronic Diseases

When your metabolic health is improved, you have a reduced risk of chronic diseases, such as diabetes, cardiovascular disease, stroke, kidney disease, and cancer, says Galati. "Studies show that even modest weight loss can improve blood pressure, cholesterol, and blood sugars."

Improved blood markers such as these can help decrease the risk, or better manage, chronic diseases. They may also help you decrease or eliminate any medications you may be on to manage these conditions.

It is important to note people at higher weights can also have healthy blood markers. The medical community tends to focus on weight and body mass index (BMI) as an indicator of health, but blood sugar, cholesterol, and blood pressure are better determinants of someone's health status than their weight alone. Weight is just one influence on many of these markers.

Increases Mobility and Joint Health

Excess weight puts stress on your joints and can contribute to inflammation, causing pain as well as wear and tear of the joint. But, losing weight may increase mobility, decrease joint pain, and reduce the risk of developing osteoarthritis. Further, staying mobile and active helps facilitate other lifestyle changes that improve health, such as increased exercise.

In one review study, patients with psoriatic arthritis who lost weight showed improved activity levels, inflammation, and pain levels. These improvements can be seen even with modest weight loss of just five to 10 pounds.

If you have joint pain, a healthcare provider can help determine the underlying cause as weight loss alone may not be the key to decreased pain. Keep in mind that pain may also hinder you from exercising, so it is important to find other strategies for pain management. Icing, physical therapy, or taking certain anti-inflammatory medications can help decrease pain so that you can engage in physical activity and take strides toward weight loss if that is your goal.

Increases Energy Levels

Larger bodies expend more energy for all bodily functions, including breathing, digestion, and physical activity. When an individual loses weight, the resting energy requirement decreases.

This often results in a boost of energy, which is often the first thing people notice when they start to change their habits and lose weight. Increased energy levels also may contribute to more desire to exercise, leading to better mental health and well-being, too.

Risks and Considerations

Weight loss doesn't come without risks, Roth says. "Individuals at a healthy weight, pregnant or breastfeeding women, those with certain medical conditions or a history of eating disorders, elderly individuals, and those with mental health conditions that may be adversely affected should be cautious about intentional weight loss."

In these cases, prioritizing nutrition and well-being over weight loss is recommended. Intentional weight loss can also harm your relationship with food, especially if you are adopting extreme diets or over-exercising to achieve it.

"Losing weight may increase obsessive food thoughts, body preoccupation, and guilt around food choices," says Galati.

Being mindful about eating enough can help you stay on track while not obsessing over food. This helps prevent extreme cravings and helps avoid slowing your metabolism. Additionally, focusing on the number on the scale could get discouraging. Rather than focusing on losing weight, hone in on behavior change and setting sustainable long-term goals.

Losing too much weight too fast also can put your physical health at risk. Rapid weight loss and not enough nutrition can lead to fatigue, electrolyte imbalances, poor digestion, reduced muscle mass, and nutrient deficiencies.

Tailoring Weight Loss to Your Goal

If you are looking to lose weight, consult with a healthcare professional and registered dietitian who can offer personalized guidance and individualized recommendations based on your specific nutrition needs. You want to go slowly and make long-term sustainable changes that will be easier to maintain.

"Simply shifting your habits and health behaviors can lead to major improvements in physical and mental health," Galati says. "You can eat more vegetables, reduce snacking on highly processed foods, and increase physical activity without weight loss being your only goal. Sometimes taking the pressure off of those numbers can help drive more positive and sustainable change."

It's also important to take a holistic approach as weight loss is multifaceted and goes beyond just what you are eating. Be sure to incorporate a combination of cardio and resistance training to help reduce muscle loss as you change your diet.

And don't neglect to address sleep and stress management. Poor sleep and high stress hormones can intensify cravings and increase appetite. Finally, include foods you love in your plan and be mindful not to restrict yourself. Learning to eat all foods in a balanced way is critical for health, weight maintenance, and enjoyment.