8 science-backed benefits of weight loss

Weight loss isn't just about weight loss. It's about all the life-changing stuff that happens as a result—from a lower risk of chronic disease to better sleep. Let's get into it.
Published 17 April 2023 | Updated 1 July 2024
WeightWatchers® member Stefanie

There are a million myths about weight loss, but one that really bothers us is that it’s some sort of vanity project. Because anyone who’s ever tried to lose more than 5 kilograms knows that, while better-fitting jeans may be a happy by-product, it’s rarely the only thing you’re after. You want less fatigue, a stronger heart, more confidence. Name something less superficial than that. Here’s how all those health benefits actually happen on the inside, plus the biggest ones you should know.

How weight loss affects health

During weight loss, you will likely lose some lean body mass (a.k.a. muscle), but the majority of the weight gone will be from losing fat. And that unlocks a whole host of health benefits. “When you have excess fat, it’s deposited in the abdomen and within internal organs, such as the liver, pancreas, and heart,” says Dr. Robert F. Kushner, M.D., professor of medicine at Northwestern University’s Feinberg School of Medicine, United States. “This visceral fat tissue increases inflammation that leads to conditions such as diabetes, hypertension, and elevated blood fats.” (Collectively, these are known as metabolic disorders.)

On top of that, extra fat puts more strain on your body. “Excess weight, especially at higher levels and for longer durations, can lead to mechanical wear-and-tear issues for the body and make the work of normal life harder,” says Dr. Jamy D. Ard, M.D., professor of epidemiology and prevention at Wake Forest University School of Medicine, United States. And you can start to see this strain even if you don’t have much weight to lose. For example, weighing an extra 5 kilograms beyond what is recommended can increase your risk for sleep apnoea.

But when you lose fat and reduce your overall weight, you can reverse the negative impact it has on your body. And that doesn’t take long to happen: Experts say that if you have overweight or obesity, losing just 5% of your body weight can make a significant difference. For example: If you’re 110 kilograms, that means losing just 5.5 kilograms can give you a lot of benefits. Here are eight important ones to get excited about:

When you lose weight, you can reverse the negative impact it has on your body—and that doesn't take long to happen. Experts say losing just 5% of your body weight can make a significant difference.

1/ Lower risk of diabetes

Having overweight or obesity raises your risk for diabetes, which is why type 2 diabetes (T2D) is 20 times more likely in people with a BMI over 35. The excess body fat raises inflammation and blunts your body’s sensitivity to insulin—a critical hormone that regulates the glucose (sugar) in your bloodstream. Because this means you need more insulin to manage healthy blood sugar levels, it puts you at risk for T2D.

But losing weight can make it easier to manage your blood glucose levels by reducing inflammation and improving how your fat, liver, and muscle tissues respond to insulin. Remember how we say it only takes losing 5% of your weight to see a major payoff? Research shows that if you have prediabetes, this is the amount it takes to potentially prevent or delay the progression to type 2 diabetes. And if you already live with T2D, losing any amount of weight can improve your body’s sensitivity to the insulin you still produce. This could potentially reduce your need for diabetes medications.

“Once someone taking insulin starts losing weight, their insulin needs go down,” explains SaRene Brooks, R.D., a certified diabetes care and education specialist at Integrated Diabetes Services in Pennsylvania, United States. “Having lower body weight means less fat stores, so your body will be more sensitive to insulin, making it easier to manage blood glucose levels.”

2/ Improved sleep and energy

The higher your BMI, the likelier you are to feel hypersomnia, or excessive daytime sleepiness, which is an urge to fall asleep during the day. Researchers aren’t entirely sure why, but they believe it has to do with poorer sleep at night due to excess fat’s impact on circulating hormones, changes in the neuronal signalling pathways in the brain, or trouble breathing (obesity can block your airways).

For some people, the impact on your airways can lead to obstructive sleep apnoea (OSA), which is a more serious condition that causes actual gaps in your breathing while you’re asleep. 70% of people with OSA are living with obesity because fat can collect in the upper respiratory tract, narrowing airways dangerously. Sleep apnoea is also linked to insulin resistance, high blood pressure, increased appetite, and depression.

Losing weight can have a huge impact on these sleep issues and, as a result, boost daytime energy. It improves breathing and sleep apnoea by lowering the pressure on your airways during the night (you reduce fat in your neck, allowing your airways to open up more). On top of that, the physical activity that is usually a part of a weight-loss program can also help you sleep better. And the benefits go both ways: Getting more sleep helps support weight loss by decreasing blood sugar, blood pressure, and your appetite.

3/ Lower blood pressure

Having overweight and obesity can up your risk for high blood pressure (a.k.a. hypertension). There are a few factors at play, but one is an increase in sympathetic nervous system activity, which causes blood vessels to become more constricted and raises blood pressure. As obesity progresses and there is more fat on the body, it can physically push on your kidneys, compressing them and making them work harder to remove waste and extra fluid from your body. This can lead to kidney burnout, where they aren’t able to remove enough fluid from your blood, increasing the volume of blood in your body and raising blood pressure.

But losing weight can take some of that load off your kidneys, as well as reduce inflammation, bringing your blood pressure back down. Research shows that losing 5 per cent of your weight can normalise your blood pressure.

4/ A healthier heart

Researchers at Johns Hopkins found that a higher BMI was linked to higher levels of troponin, an enzyme in the blood that raises your risk for having a heart attack. Those whose BMI was 35 or higher had the highest levels of troponin and were nine times more likely to develop heart failure than those with a healthy BMI and low levels (or no levels) of troponin.

“A consequence of excess fat is that lipid levels are high, such as total cholesterol, LDL cholesterol, and triglycerides,” says Ard. “And when those high lipid levels are combined with high inflammation, it creates an environment where artery-clogging plaque can form easily.”

Losing weight can reverse that. A 2018 Swedish study found that people who lost weight gradually and kept their BMI at a healthy level had stronger left ventricular systolic and diastolic functions (that’s basically the heart’s pumping mechanism) when compared with study participants who were still living with overweight or obesity.

5/ Reduced risk of cancer

The American Cancer Society reports that excess body weight contributes to about 11.9% of cancers in men and 13.1% in women. The extra fat tissue can increase your risk of many different types of cancer, including endometrial, kidney, liver, thyroid, pancreatic, and breast (in post-menopausal women). Research has also determined that your risk of death caused by cancer is significantly higher if you have obesity.

The connection between excess body weight and cancer risk is not fully understood, but insulin resistance, increased oestrogen levels, and inflammation resulting from excess fat are all thought to play a contributing role. “Excessive fat tissue can have an impact on inflammation in the body, affecting levels of certain hormones–like insulin, insulin-like growth factor, and sex hormones–which can impact how our body functions,” says Michelle Cardel, Ph.D., R.D., senior director of global clinical research & nutrition at WeightWatchers.

6/ More interest in sex

Living with overweight or obesity can impact blood flow, hormone levels, and other functions which play a role in both your sex drive and ability to enjoy sex. For example, carrying around excess body weight can significantly decrease your testosterone production—affecting the sex drive in both men and women. It also negatively impacts blood flow, which is needed for arousal.

Weight loss, however, has been shown to improve your libido and ability to orgasm. It improves your cholesterol and triglyceride levels, which then decreases plaque build-up in your blood vessels and improves blood flow all over, including your genitals. This can make it easier for people to achieve and maintain an erection or produce vaginal lubrication, making intercourse more enjoyable.

7/ Less achy joints

Having overweight and obesity raises your risk for osteoarthritis, which is when cartilage around a joint gets worn down, causing pain and making it tough to move. For example, every 5 kilograms of weight you gain increases your risk of knee osteoarthritis by 36%. And it’s not just knee joints that bear the brunt of it. Pain can pop up in joints all over your body.

“Excess weight on your skeletal frame negatively impacts your physical function,” says Ard. “It can increase your risk of injury and damage to the structures of your joints.” Reducing body fat can lower the physical stress on your joints as well as inflammation, which also contributes to osteoarthritis.

8/ Better mood

Rates of depression are twice as high in people with obesity than those considered “healthy weight.” This link is due to things like the stigma and discrimination around obesity and the risk factors shared by the two conditions, like poor sleep and not being physically active. There’s also an actual cause-and-effect happening, with the inflammation brought on by obesity raising your risk for depression. A similar thing happens with anxiety, which is more likely to happen to someone with obesity.

While anyone with clinical depression and anxiety should get help from a professional, losing weight can also help improve symptoms. And even if you don’t have a clinical diagnosis, the psychological benefits of weight loss reach far and wide, says Dr. Fatima Cody Stanford, M.D., a specialist in obesity medicine at Massachusetts General Hospital, United States. Research shows that people who lose 5% of their body weight report feeling generally happier and better about themselves overall. This might show up as improved confidence and self-worth or more courage to try new activities.

How to lose 5% of your body weight

That’s the number many experts recommend if you want to see the above kinds of benefits. Here’s how to lose weight:

  1. Start tracking. Tracking is the cornerstone of the WeightWatchers program for good reason–it works. Tracking what you eat can make you more aware of your food choices because you’re less likely to mindlessly eat. In fact, consistent tracking (15-20 minutes a day) of food was found to result in a 10% loss of body weight during a 6-month online behavioural weight loss program.

  2. Handpick your support system. The more support you get from friends and family, the more weight you’re likely to lose. One reason why: Research suggests that people tend to interpret roadblocks as being less challenging when they feel supported by others. For example, one study found that when people stood at the bottom of a hill, it appeared 10-15% less steep when they were with a friend compared to when they were alone. To get the support you need, WeightWatchers offers Connect groups, plus virtual and live Workshops.

  3. Prioritise activity. Researchers have discovered that being active is the single greatest predictor of who keeps weight off and who doesn’t. Small steps can make a big difference here, so go on a 20-minute walk after lunch, use a fitness tracker to log steps and have a goal in mind, and sign up for a new fitness class that you’ve always wanted to try.

  4. Manage stress. Because it can trigger higher levels of cortisol and a desire to eat comfort food, chronic stress can make it harder to lose weight. You can’t just snap your fingers and create a stress-free life, but you can experiment to see what kinds of calming activities work best for you. Maybe it’s listening to a guided meditation app, intentionally removing responsibilities from your plate, or speaking to a mental health expert.

  5. Improve your sleep. When you don’t get enough sleep, you have higher levels of the hunger hormone ghrelin and lower levels of leptin, which is linked to feeling full. Feeling tired can also make it tougher to find motivation to exercise. One of the best things you can do for sleep is to have a set schedule, meaning you go to bed and wake up around the same time every day (weekends included).

As always, it’s a good idea to talk to your healthcare provider if you want to lose weight or if you try the above and aren’t seeing the results you want.

As excited as you might be to see all the above benefits (and all the other non-scale-related victories that come with weight loss), remember that the average recommended weight loss for an adult is about 0.5 to 1 kilogram a week. It’s important to start small and set realistic goals—and be kind to yourself in the process.

This content is for informational purposes only and does not constitute medical advice, diagnosis or treatment. It should not be regarded as a substitute for guidance from your healthcare provider.