Barnes-Jewish Hospital | Washington University Physicians
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Originally published Jan 2023

Photo courtesy of Shutterstock
By Connie Mitchell
Weight Loss: It’s Not Magic, It’s Math


No carbs! No fat! Hack your metabolism! Take a supplement! Exercise it off! Eat once a day! Fast once a week!

The marketing messages hit you from all directions—television, magazines, social media. There are apps for weight loss and websites and books and online programs. It’s big business, and the quantity of often conflicting information can be confusing and overwhelming. And the truth is, many of these weight-loss schemes are based on scant medical evidence. Could it be true that there simply is no magic bullet?

“It’s important to understand that obesity is a chronic disease,” says Samuel Klein, MD, Washington University weight-loss specialist at Barnes-Jewish Hospital and founder of the university’s Weight Management Program. Obesity, typically defined as a body mass index (height-to-weight ratio) of 30 or more, afflicts more than 40% of American adults, according to the Centers for Disease Control and Prevention. “If you don’t address the disease, you’re not going to have any beneficial impact on it. And don’t blame yourself. The truth is we’re all genetically predisposed to being overweight or obese,” Klein adds.

Our genes ensured the species’ survival by helping the body store excess calories as fat that could be used when food was scarce. “Those genes have turned against us in this environment, where food is plentiful, companies know how to get us to eat more than one chip, and most social activities involve food,” Klein says.

Essentially, our genes have been tricked by rapid environmental changes.

That doesn’t mean, however, that losing weight is a losing proposition. “Losing even a little bit of excess weight can have very important clinical benefits,” Klein says. He also emphasizes that changing one’s diet can improve overall health, decreasing the risk of cardiovascular disease, diabetes and cancer, even if body weight doesn’t change.

And that’s the message he shares with patients: Learn what constitutes healthful eating, then make a plan, and follow it—no matter what you weigh. A small change can make a difference.

For those who do want to lose weight, take heart. You can bypass all the false promises and distractions if you understand the science.

Calories in, calories out

No matter what you’ve heard, Klein says, the basics of your body’s energy balance—calories in, calories out—are the foundation for a healthy weight. Even small changes in calorie consumption will affect weight over time. “If you eat one more Life Saver a day than you’re eating now, an addition of about 10 calories, you’ll gain a pound of weight over three years, and half of that would be gained in the first year,” Klein says. “If you eat a candy bar every day, about 240 calories, to give yourself a little boost, you’ll gain 24 pounds in three years.” Conversely, eating one less candy bar or Life Saver will result in weight loss.

Determining a person’s caloric needs depends on several factors, including age, metabolic profile, activity level, height and weight, hormonal fluctuations and the presence of any prescription medications that can contribute to weight gain or loss. Adding all that up makes for a complicated equation.

In that equation, Klein says, “’metabolism’ is kind of a wastebasket term. You have to be more specific. What you’re really talking about is energy expenditure.” Daily energy expenditure includes resting metabolic rate, physical activity and digestion of the food we eat.

“Those components vary from person to person and are based on body composition and genetics,” Klein says. “You may be the same size and body composition as another person, but you could have different resting metabolic rates determined by some unknown genetic factors.” You’ll each burn calories differently while performing routine daily activities. Energy metabolism, in other words, is highly variable.

The 2015-2020 Dietary Guidelines for Americans recommends 1,600 to 2,400 calories per day for women and 2,000 to 3,000 calories for men. That’s a wide range. To understand your specific calorie requirements, Klein recommends making an appointment with a specialist in obesity medicine, who can complete an assessment.

Even once the math is done and a calorie goal is set, the formula often fails because changing dietary habits and reducing calories are hard to maintain consistently over time. Simply tracking calories to meet an intake goal is a very difficult task, Klein says. “No one can stick with old-fashioned calorie counting long-term, but there are new tools to help people maintain and regulate their body weight, and many of those are accessible using smart devices.”

For instance, a smart scale can be programmed to send updates on weight and body composition to a designated health-care provider, a valuable tool for those under medical supervision. Whether you have a smart scale or not, Klein suggests monitoring weight daily and making small adjustments to diet as needed if you notice your weight creeping up.

Making calorie and diet changes can be easier using a food-tracking app. “There are programs that provide automatic internet feedback every day, with advice and encouragement based on an initial form you fill out about your goals and habits,” Klein notes. “Self-monitoring is key to any lifestyle change, so weighing yourself and using an app that helps you stay mindful can help.” Nevertheless, he adds, none of the many, many devices and apps available offer any credible scientific evidence that they can make a lasting difference. And many people lose interest after a few weeks.

Making change stick

Self-monitoring may be all that’s needed for some motivated individuals to stick with a diet plan and achieve weight-loss success. But many people struggle to adhere to new eating habits, and that’s where Richard Stein, PhD, Washington University psychologist and behavioral director of the Weight Management Program, comes in. Working within that program, Stein performs behavioral evaluations of patients and oversees weight-loss support groups.

“People don’t realize how many food-related occasions there are in American culture. They think, ‘Once I get through the holidays into January, I’ll be fine,’ but then there’s the Super Bowl party, Valentine’s Day dinner, Mother’s Day brunch. It’s always something,” Stein says.

A single splurge—or two—don’t have to derail a weight-loss effort, but Stein often sees people quickly give up for days or weeks after a diet stumble. The most effective response is to put the slice of pie or other indulgence behind you, and resume a healthy diet as soon as possible, he says. “Every day, every meal, every mouthful is a new decision.”

Stein also encourages individuals to find ways other than food to reward or care for themselves. Develop a list of alternatives as rewards: a spa treatment, a walk with a friend, deep breathing exercises or making an entry into a journal of life’s ups and downs. All will get you closer to a goal than a celebration laden with calories. Participants in the Weight Management Program’s support groups receive a list of “101 Ways to Take Care of Yourself” to help spur ideas.

It’s also important to set up your daily environment and routine to support your goals, a technique known as stimulus control. Remove temptation and plan for ways to avoid pitfalls. For example, use online grocery shopping to avoid impulse buys of calorie-rich food at the store, and purge your home and office of any foods you want to avoid. Create a route to the office that doesn’t take you past vending machines or drive-thrus that have been more than you could resist in the past. Some people respond to signs they’ve placed in strategic locations—the door to the fridge, a full-length mirror—that remind them to stop and think before reaching for additional calories.

“If you have to have something that you know isn’t part of your healthy-eating plan, then force yourself to have it outside the home,” Stein adds. “If you’re craving ice cream, drive to an ice cream shop; don’t buy a gallon of ice cream and put it in your freezer.”

Stimulus control also can promote desired behaviors. For example, if ready-to-eat vegetables and hummus are placed in clear containers at eye level inside the refrigerator, they can prompt you to snack on them instead of a less-healthy choice. Running or walking shoes placed right inside the door can serve as the prompt to head out to get some air and exercise.

Pairing stimulus control with accountability can result in an especially effective strategy. Stein recommends sharing goals with a friend, family member, medical professional or support group and reporting progress on a regular basis. You’ll be accountable for your actions—and you’ll be enlisting support from others.

Stein notes that, when using these and other tactics, most people can change behaviors and create new, healthier habits, despite cultural, family and social histories revolving around food. He also acknowledges the difference between healthy behaviors and a genetic propensity to carry excess weight. Eating may feel like an addictive behavior to some people, but the evidence is still evolving on this point, he adds. “The field is beginning to consider the possibility of food addiction, but the science is still developing.”

More weight-loss options

In some instances and for some people, behavioral changes just aren’t enough to achieve weight loss. Prescription weight-loss drugs and surgical procedures are available for adults with high-risk health concerns related to obesity.

These options do not replace a healthy diet and lifestyle program, however. Rather, they serve as additional tools to help those with a critical need for weight loss. Diabetes and high blood pressure are two of the most common medical conditions with known correlations to excess weight. When these are present in someone with obesity, medical and surgical treatments may serve as viable options.

“The landscape of medical interventions for obesity has changed dramatically in the last few years,” says Susan Reeds, MD, Washington University weight-loss specialist at Barnes-Jewish Hospital and medical director of the Weight Management Program. Once the medical community recognized obesity as a chronic disease, treatment approaches began to evolve. Newer medications for weight loss are safe and effective, although insurance companies are slow to approve them, which limits access for some. “Insurance coverage is the number one roadblock in helping patients obtain these medicines,” Reeds says. “It’s a significant problem.”

One class of drugs, initially used to treat diabetes, works to modulate insulin resistance; people with diabetes who were taking these prescription drugs lost weight. Now, these medications are also used to help people with obesity. The average weight loss is about 15% of body weight—enough to make a significant difference in overall health, Reeds says. People with a BMI of 30 or greater, or a BMI of 27 or greater plus medical comorbidities—may benefit from this medication.

Not that long ago, physicians traditionally viewed surgical interventions for weight loss as a last resort. Vladimir Kushnir, MD, Washington University gastroenterologist at Barnes-Jewish Hospital, uses a procedure called bariatric endoscopy to treat obesity, noting it can be a good option for those who qualify for the procedure. “We know that weight-loss surgery can be associated with a rapid reversal of diabetes and other obesity-associated comorbidities,” he says. Insurance may cover weight-loss surgery for people with a BMI of 35 or greater who also have a medical comorbidity, including high blood pressure, arthritis or diabetes, or for people with a BMI of 40 or greater with no other diagnoses.

Today’s weight-loss surgery is minimally invasive and is almost exclusively performed laparoscopically. On average, patients lose 25% to 40% of their body weight within a year. An even less-invasive option involves suturing a portion of the stomach closed via an endoscope inserted through the mouth; this treatment can result in about a 10% to 15% weight loss.

A newer, reversible procedure places a balloon into the stomach, inflating it to create a feeling of fullness; the balloon can later be removed. This procedure carries less risk than more invasive surgeries. "We’re also involved in a clinical trial in which the patient swallows a balloon, which then deflates and comes out after about four months,” Kushnir says.

A surgical procedure, however, doesn’t mean an end to watching calories and working to burn them. Kushnir says, “If someone continues the caloric intake that was typical pre-surgery, weight loss won’t take place. You will still have to make ongoing changes to diet and lifestyle.”

Strive for healthy, not skinny

No matter what approach you take to achieve and maintain a healthy weight, Klein emphasizes the importance of focusing on a healthy lifestyle in general. Currently, scientific data is scant for the benefits of any one diet or intervention, and the best diet is the one you’ll stay on long-term that delivers nutrients you need without excess calories.

When asked about popular diets, such as those that restrict carbohydrates or fat or those that require intermittent fasting, Klein notes that long-term compliance is problematic for most of these, and data have not shown any significant benefit unrelated to overall calorie consumption. In other words, restricting carbs might decrease overall caloric intake, and that results in weight loss.

 “We are studying the metabolic benefits of various diets, given the same amount of weight loss or no weight loss at all,” Klein says. “We provide participants with all the food for specific diets, which improves compliance.”

However, researchers continue to explore the science of weight loss. Currently, the research team is comparing a low-carb diet, a low-fat diet and what’s known as the Mediterranean diet. Obese individuals who participate undergo a complete cardio-metabolic evaluation and receive compensation for their participation.

“We’re also trying to understand why some people with obesity are metabolically unhealthy and others are not by identifying mediators in the bloodstream and evaluating them,” Klein says. Klein describes one such marker, called small extracellular vesicles, as “little balls surrounded by a lipid coating so they can circulate in the bloodstream. They’re made by every cell in the body, and they deliver cargo from one cell to another. We think they might be involved in transmitting either adverse or beneficial effects of obesity in unhealthy or healthy people with obesity.”

For now, given what science has uncovered about weight and weight loss, each of us has the option to choose a healthy lifestyle. “Help is available if you need it,” Klein notes. “You needn’t be embarrassed. If you need help managing the chronic disease of obesity, seek it. You’re likely to live a longer, healthier life as a result.”


Schedule an appointment or learn more about the Washington University Weight Management Program; visit or call 314-286-2080.

Learn more about weight-loss surgery by watching an online seminar.

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