The Science Behind Losing Weight and Keeping It Off

March 28, 2023 Posted by AHW Endowment

A body weight scale displays a number; AHW shares the science behind losing weight.

Nearly one-third of Wisconsinites are obese. Considering the many health risks and challenges associated with obesity, it should come as no surprise that the science behind losing weight and how to successfully drop pounds is an ongoing topic of interest. While there are countless diets and weight loss plans to choose from, finding a strategy weight loss strategy that works—and, keeping the weight off—can be difficult for many.

In a recent Coffee Conversations with Scientists episode, Tammy Kindel, MD, PhD, bariatric surgeon and associate professor at Froedtert and the Medical College of Wisconsin (MCW), explained the science behind losing weight, why sustaining weight loss can be so challenging, and how bariatric surgery helps some patients live healthier lives.

What is Obesity and Why Is It a Danger to Your Health?

In Wisconsin, 65% of residents are overweight with a body mass index (BMI) of 25 to 30, or obese with a BMI over 30. Generally, obesity is caused by a person consuming more calories than they expend (or “burn”). Factors such as lifestyle, environmental influences, and genetics also contribute to obesity.

Why is obesity dangerous to your health? It’s a risk factor for many serious health conditions and diseases, including:

  • Type 2 diabetes
  • Infertility
  • High blood pressure
  • Heart disease
  • Breast, colon, and endometrial cancers
  • Stroke
  • Gallbladder disease
  • Fatty liver disease
  • High cholesterol
  • Breathing problems, such as sleep apnea
  • Chronic lower back pain
  • Arthritis
  • Osteoarthritis

Unfortunately, certain populations are more susceptible to associated health risks than others. “Individuals who are growing up in areas with high community stress, low socioeconomic status, and not a lot of access to food resources and nutrition education are certainly more at risk for gaining weight and having more significant medical complications associated with being overweight,” said Dr. Kindel.

Losing weight is essential for obese patients to improve their health outcomes. According to the Centers for Disease Control and Prevention, reducing your body weight by just 5 to 10% can support better blood pressure, blood cholesterol, and blood sugars, among other health benefits.

Untitled design (11)

What’s the Science Behind Losing Weight?

Losing weight, or body weight regulation, requires adjusting a person’s caloric intake and the number of calories they expend. When more calories are expended than consumed, the body experiences a calorie deficit that causes weight loss. While the formula seems simple, many factors influence our caloric intake and output.

According to Dr. Kindel, “There are multiple mechanisms that control food intake through signals, in our brain and our periphery, that give us signs for hunger and satiety (feeling full) … Our body also regulates the burn (the output), and it does that through our metabolic rate and how it’s controlled by hormones, medical conditions, and medications.”

There’s more to the science behind losing weight than counting calories in and calories out. Making healthy changes to your diet (such as adding more greens and whole fruits and reducing sugary drinks and trans fats) and focusing on regular moderate physical activity are important to not only losing pounds but also maintaining weight loss.

Why Is Weight Loss Difficult to Maintain?

Once a person achieves their weight loss goal, keeping the weight off is not always easy. Many who lose a significant amount of weight will regain that weight within two to three years of losing it. So, why is it so challenging to sustain weight loss?

It’s not uncommon for people to make significant changes to their diet, exercise, and lifestyle habits to lose weight. This might include minimizing or cutting out certain food groups and engaging in more frequent or different types of exercise. However, once the desired weight loss is achieved, maintaining the weight loss hinges on continuing those habits and lifestyle changes.

During the CCWS episode, Dr. Kindel discussed a study on exercise, metabolism, and weight involving contestants on the popular weight-loss-focused reality television show, “The Biggest Loser.” Researchers found that many individuals who succeeded in long-term weight loss and maintenance after the show had a significant metabolic adaptation: meaning, even years after the competition, they had not resumed a normal metabolic rate. This suggests that their ability to keep the weight off after their time on the show is due to continuing diet and exercise routines like what they practiced during the competition.

Dr. Kindel commented that sustaining the diet and activity changes made to achieve weight loss is critical to maintaining it. “Significant weight loss is not necessarily driven by just cerebral cortex by willpower. There are a lot of signals at play. We can’t necessarily control our metabolic rate, so the guiding principle I took away as a clinician from the study is that what gets you there (in a diet) keeps you there.”

What is Bariatric Surgery and Who Is It For?

Bariatric surgery is an approach to weight loss that reduces the size of the stomach, which can help reduce food consumption. For some patients, bariatric surgery is the best strategy for long-term weight loss and better health.

Regarding who is eligible for bariatric surgery, Dr. Kindel said, “You could be considered a candidate if your body mass index is 30-35 if you have an obesity-associated medical condition… If your body mass index is 35 or higher, there’s a cardiovascular risk reduction, even if you haven’t developed one of those medical problems yet, where we feel the risk of surgery is less than long-term untreated obesity.”

The two most common bariatric surgeries performed at Froedtert and MCW are a Sleeve Gastrectomy and a Roux-en-Y Gastric Bypass, which alter a body’s signals regarding food intake, the amount of food it takes to feel full, and can reduce hunger hormones. The type of bariatric surgery that is best for an eligible patient depends on factors such as the patient’s medical conditions, BMI, and preferences.

To make bariatric surgery experiences and life afterward better for all Wisconsin patients, Froedtert and MCW’s Medical Weight Loss and Bariatric Surgery Program have taken steps to ensure patients have access to essential resources for success.

Researchers conducted a survey that established 38% of the program’s patients, regardless of whether they are insured, experience food insecurity (not having enough or adequate food for a healthy life). This led to the introduction of food insecurity screening for all bariatric surgery patients to ensure quality care for patients with any socioeconomic status.

Before any bariatric surgery, the program’s patients must complete a two-week protein shake diet to reduce the size of the liver and minimize risks due to surgery. To help every patient access and benefit from the protein shakes this process requires, the Medical Weight Loss and Bariatric Surgery Program started a protein shake food bank where patients can donate and take home unopened and unused protein powders.

Screenshot (45)

(Courtesy of MCW Department of Surgery, Division of Minimally Invasive Gastrointestinal Surgery)

Finding the Right Approach for Losing and Maintaining Weight

Regardless of what weight loss plan you decide is right for you, Dr. Kindel suggests these guiding principles for weight management:

  • Try not to drink calories (juice, sugary coffee drinks, alcohol, etc.);
  • Track your diet and habits to increase your accountability; and
  • Find an aerobic activity for cardiovascular health you enjoy, and add strength training for muscle mass.

When it comes to finding an approach to losing weight that will be successful, what’s most important is to be realistic about your lifestyle and what changes you’ll be able to maintain in the long run.

You can view the full CCWS episode about the science behind losing weight with Dr. Kindel here:



Subscribe to Advancing Health Now