What Your Doctor Gets Wrong About Losing Weight

Weight loss is a controversial topic. Steeped in myths and misconceptions, the issue has been long misunderstood within the medical community, say researchers (via Cureus). Being overweight has been blamed for a number of health conditions from diabetes to cardiovascular disease to sleep disorders, while calorie restriction dieting has been recommended as a practical method for achieving weight loss and maintenance. 

But a number of studies are now showing that some of these assumptions are flawed. The relationship between weight and health is deeply complex. 

The Health at Every Size (HAES) paradigm suggests that our culture shifts its focus from weight loss to encouraging people to develop healthy habits like eating nutritious foods and exercising more instead — an approach that's been shown to lead to improvements in physical and mental health, as well as psychosocial outcomes (via Nutrition Journal). Here are some things about losing weight that doctors have historically overlooked or gotten wrong. 

Weight loss isn't always as simple as eating less and moving more

We've heard it many times before: If you want to lose weight, simply eat less and move more. Many physicians subscribe to the "calories-in-vs.-calories-burned" mantra for weight loss (via TIME). And while it makes perfect sense in theory, studies and anecdotal reports continue to inform us that shedding weight in the long term isn't quite as straightforward as that for everyone (via Nature Medicine). There are many different factors that can prevent a person from losing weight despite eating less and exercising more, including their own unique metabolism, hormones, gut health, lifestyle choices, and the types of foods they eat — not just how much of them. 

Highly processed and refined carbohydrates like bread, cakes, and cookies spike insulin levels that cause fat cells to soak up calories, according to a study published in the 2018 issue of The BMJ. This means that your body stores fat more easily when you eat these foods. Excess insulin levels also lead to increased hunger and food cravings, making it harder for people to lose and keep weight off. The study lends support to the idea that the types of calories people consume along with individual differences in biology may influence how people respond to weight-loss diets in the long term.

There's no one-size-fits-all approach

A doctor may prescribe the same diet plan to different patients. But losing weight is an individualized process that differs from person to person, claim researchers. "You take a bunch of people and randomly assign them to follow a low-carb diet or a low-fat diet," Kevin Hall, a scientist at the National Institutes of Health (NIH), told TIME. "You follow them for a couple of years, and what you tend to see is that average weight loss is almost no difference between the two groups as a whole. But within each group, there are people who are very successful, people who don't lose any weight, and people who gain weight."

The same weight-loss plan may yield different results for different individuals depending on their unique genetic composition. Even identical twins, who have pretty much the same DNA, can have very different responses to the same foods, notes a 2020 study published in Nature Medicine. The researchers discovered a vast array of metabolic responses to eating. For instance, some people metabolize food better in the mornings than others. Foods that cause one person's blood sugar to skyrocket may not have the same effect on another, while specific foods and diets can trigger inflammation in healthy adults in unique ways.

Weight loss diets often fail

A low-calorie diet is often recommended for quick weight loss if a patient's weight is believed to be the cause of a serious health problem (via MedlinePlus). However, research shows that low-calorie diets can have a number of negative health consequences and side effects including fatigue, constipation, dehydration, diarrhea, bad breath, and hypoglycemia (via Nutrition and Diabetes). 

Most diets pose more drawbacks than benefits, which naturally cause people to throw in the towel, notes a 2020 review study published in The BMJ. A very low-calorie diet, in particular, can sabotage your metabolism, according to research from the journal Environmental Health and Preventive Medicine. This means that people generally lose weight far slower than those following a moderately low-calorie diet. A key reason for this is that consuming too few calories causes the body to overcompensate by slowing down your metabolism and efficiently storing more fat. It can also heighten cravings and cause people to overindulge in the foods that they've been trying to avoid. 

Thus, any weight loss that occurs from heavily cutting back on calories is usually temporary, triggering a yo-yo effect — also known as "weight cycling" — wherein people get caught up in a loop of losing weight quickly, putting it all back on again, and then attempting to lose weight again by dieting (via BMC Research Notes).

Weight loss doesn't necessarily equal better health

For years, mainstream medical advice and diet culture have been telling us that extra body fat is inextricably linked to ill health. Yet, some researchers argue that weight and health are not synonymous (via International Journal of Behavioral Nutrition and Physical Activity). 

While there's some evidence that obesity is associated with the risk of certain diseases like diabetes and heart disease, it's entirely possible to be unhealthy in a slim body and healthy in a fat body (and vice versa). Losing weight on its own won't necessarily improve your health. What's more important is that a person is "metabolically sound" — that is, they have optimal levels of blood sugar, blood pressure, cholesterol, waist circumference, and triglycerides, based on the results of a study from the European Heart Journal. Another 2016 longitudinal study found that individuals who were lean but unfit were twice as likely to get diabetes than those who were fat and fit (via Obesity).

The number on the scales isn't always helpful

Doctors have been using body mass index (BMI) to determine whether a patient is a "normal" weight for decades. Many researchers now consider this measurement to be flawed and outdated (via International Journal of Obesity). 

One reason for this is that BMI is used as a quick reference that doesn't differentiate between body fat, muscle, water, or any other component of the body — it's simply calculated by dividing a person's weight in kilograms by their height in meters squared. So, a muscular person with low health risk could be wrongly categorized as overweight because they have a high BMI. On the flip side, a person who is thin but has a high percentage of body fat — and therefore, a higher health risk — may be seen as being at a healthy weight. 

Research shows that BMI is largely based on what's considered healthy for Caucasian body types and doesn't consider a person's race or ethnicity (via The New Zealand Medical Journal). For this reason, a report by the UK Parliament Women and Equalities Committee recommended that health professionals ditch BMI as a tool for estimating healthy body weight.

Restrictive diets can be detrimental to your mental health

A low-calorie diet may have specific benefits in certain cases and when closely monitored by a healthcare professional (via European Review for Medical and Pharmacological Sciences). But there's also evidence that restricting foods you love can take a pretty harsh toll on your mental health. 

When people feel deprived, they tend to feel stressed, which ultimately goes against weight loss, points out a study from the journal Appetite. Stress triggers the adrenal glands to release cortisol, a steroid hormone and your body's natural stress alarm. Elevated cortisol levels can disrupt and wreak havoc on the processes that it normally regulates such as your metabolism, sleep-wake cycle, and blood sugar and insulin levels, which can lead to increased food cravings and overeating.

Counting calories and rapid weight loss can have a number of negative psychological effects. One study found that dieting leads to psychological deprivation that's similar to what people experience when they starve (via Journal of the American Dietetic Association). This can cause obsessive thinking around food and disordered eating behaviors including a cycle of restricting and bingeing. It can also mess with your internal hunger cues, since a large amount of time is spent overlooking and thwarting your body's natural signals (via Cureus).

Weight loss isn't simply a matter of self-control

Losing weight is no easy feat. Despite long-term efforts and consistent motivation, many people struggle to reach or sustain their weight loss goals, and most of them regain much of the weight they lost while dieting (via Cureus). The problem with the simplistic idea that people can lose weight by eating less and moving more or following a standard diet plan is that it can lead to the assumption that the failure to lose weight is due to a lack of self-control and discipline. But research shows that the real reason may be grounded in basic human physiology.

Self-discipline can be a powerful tool, but weight loss doesn't merely come down to willpower, suggests a study published in the New England Journal of Medicine. Hunger-related hormones such as leptin, ghrelin, insulin, amylin, cholecystokinin, and peptide YY make it hard for people to keep the weight off, as the body has a natural weight (also known as a "set point") which it's programmed to return to, even up to a year after weight loss. So, dieters are working against their body's natural biological signals and functions. 

Having a more realistic view of the challenges of weight loss can yield better outcomes (via American Journal of Clinical Nutrition). What's more, rather than focusing on internal willpower, changing your external food environment can bring about higher cognitive restraint and achieve greater weight loss in the long term.

Eating healthily is more beneficial than a weight loss diet

The idea that losing weight will improve health is a commonly held belief among many healthcare professionals (via Nutrition Journal). But a person's weight doesn't necessarily tell us an accurate story about their health. In fact, there's evidence that the focus on weight and weight loss can do more harm than good -– weight bias has even been known to lead to misdiagnosis (via Health). 

Some doctors recommend a low-fat diet for weight loss, since fat has more than double the calories per gram as carbohydrates (via Cleveland Clinic). Not only are such diets ineffective for healthy weight loss, but they may not be all that good for us, report researchers (via The Lancet Diabetes & Endocrinology). A study from the journal JAMA Internal Medicine discovered that people who consumed a high-fat diet had 16% lower premature death rates compared to those who followed a low-fat diet. After all, many high-fat foods like avocado, nuts, and olive oil are actually super healthy.

"We need to look beyond the ratios of calories from fat, carbs, and protein to a discussion of healthy eating patterns, whole foods, and portion sizes," Deirdre Tobias, a researcher at Brigham and Women's Hospital, told Harvard T.H. Chan School of Public Health.

Fat shaming is harmful to health

The rampant emphasis on losing weight could be having a more harmful impact on health than obesity itself, some experts argue. "Perhaps the idea that fat is undesirable has been so deeply drilled into our minds as doctors, that it is challenging to consider that something else could be worse," note the authors of a study published in the journal Cureus, adding that it's important for health professionals to consider the physical and psychological effects of "chasing after weight loss." 

Weight bias at the doctor's office isn't merely the cause of hurt feelings. It's been shown to jeopardize patients' efforts to lose weight and has been linked to a number of health risks and higher mortality rates, point out researchers (via Canadian Medical Association Journal). A study published in the journal Obesity revealed that people who internalize weight stigma have increased levels of the stress hormone cortisol, which may play a role in perpetuating the vicious cycle of weight gain while making them sick in the long run.

Gut bacteria vs. Counting calories

When it comes to the question of why a specific diet may work for one person and not another, the answer may lie in an individual's gut microbiomes, suggests a 2019 study (via Scientific Reports). Researchers discovered that the types of bacteria in your gut may have more to say about how much visceral fat you carry –- a type of fat stored deep inside your belly –- than what you eat. A low-calorie diet could actually be doing a number on your gut health, notes a 2021 study (via Nature). The foods that people generally eat when following a low-calorie diet alter the composition of the microbiota in the gut, increasing the harmful strains of bacteria that cause diarrhea and colitis.

A diet that leads to a healthier gut community may promote sustainable weight loss. This could also explain why identical twins respond to the same foods differently despite sharing much of the same DNA, since they share just 37% of their gut microbes, according to research published in Gastroenterology. Besides your gut microbes, your weight is influenced by the types of minerals and nutrients you consume rather than the number of calories, per Scientific Reports. 

"When you solely focus on weight, you may give up on changes in your life that would have positive benefits," Kevin Hall, a scientist at the National Institutes of Health (NIH), told TIME. More investigation is needed to bring light to the role of gut microbes in health.