For millions of individuals around the world struggling with chronic weight management and type 2 diabetes, the standard medical prognosis has long felt like a life sentence. Patients are frequently told by their physicians that their metabolic conditions are permanent, progressive, and irreversible, leaving them with little recourse other than a lifetime of medication management.
However, prominent nephrologist and New York Times bestselling author Dr. Jason Fung has spent years challenging this conventional narrative. Through his clinical observations, extensive writing, and public advocacy, Dr. Fung has worked to prove that the traditional approach to metabolic disease is fundamentally flawed. His central message is clear and disruptive to decades of dietary dogma: the real problem underlying the global obesity and diabetes crises is not simply a matter of counting calories, but rather how the body processes and responds to insulin.
Understanding this vital distinction, experts argue, could fundamentally transform how modern medicine and individuals approach the prevention and treatment of obesity and type 2 diabetes.
Type 2 Diabetes Is Reversible—Despite What You’ve Been Told
For decades, the medical establishment operated under the firmly entrenched teaching that type 2 diabetes was an inherently chronic and progressive disease. Once an individual received a formal diagnosis, medical textbooks and practitioners maintained that the condition would remain with them for the rest of their lives. Patients were routinely informed that there was nothing they could do to truly eliminate the condition, and that their only option was to manage advancing symptoms through pharmaceutical interventions.
“During training, all through medical school, doctors basically get told over and over again that it’s a chronic and progressive disease,” Dr. Fung explains, describing the traditional medical education framework. “Once you have it, you have it for life. You’ll never get rid of it and there’s nothing you can do but take your medications.”
Yet, real-world clinical evidence frequently suggested a different reality. Across various observational settings, patients who achieved significant weight loss consistently saw their diabetes symptoms improve dramatically, sometimes disappearing entirely. Despite these persistent real-world observations, it was not until 2023 that the American Diabetes Association officially incorporated formal criteria for diabetes remission into its clinical guidelines, finally acknowledging what many patients and independent clinicians had observed for decades.
Reflecting on this long-overdue shift in institutional policy, Dr. Fung points out the striking delay in official recognition. “It was so obvious that it was so untrue that they finally put in criteria for remission in 2023,” he notes. “From the 1960s until 2023, the American Diabetes Association put on its website that this is a chronic and progressive disease. And then finally in 2023, only like 3 years ago, they finally admitted, ‘Oh, hey, actually it can go in reverse.’”
The underlying issue, according to Dr. Fung, was never that the reversal of type 2 diabetes was biologically impossible. Rather, the fundamental flaw lay in the fact that the medical community was attempting to use pharmaceutical drugs to treat what is fundamentally a dietary disease.
Why the Calorie Model Fails
When individuals seek guidance on how to lose weight or improve their metabolic health, the advice they receive almost invariably boils down to a single mathematical equation: calories in minus calories out equals body fat.
On the surface, this model sounds entirely logical and scientifically sound. The common prescription is simple: eat less food, move more throughout the day, and the body will naturally shed excess weight.
However, Dr. Fung argues that this simplistic thermodynamic model overlooks the most critical regulatory mechanism in the human body: hormones.
“For every calorie you eat, your body can either store it or it can burn it,” Dr. Fung explains, breaking down the biological limitations of the calorie-counting model. “Which one does it do? It doesn’t depend on the number of calories. It depends on the hormones that tell your body whether to store it or to burn it.”
To illustrate this physiological reality, consider what happens when a person consumes a snack consisting of two cookies. That specific food choice triggers a rapid and significant spike in insulin. The elevated insulin acts as a chemical messenger, instructing the body to store those incoming calories as adipose tissue, or body fat. Meanwhile, the body’s vital organs—such as the heart, lungs, and liver—fail to receive the immediate energy they require from the circulating bloodstream.
As a consequence of this hormonal signaling, a distinct biological chain reaction occurs. The individual remains hungry because their cells have been denied accessible energy, prompting them to consume more food, such as more cookies, thus perpetuating a relentless metabolic cycle.
In contrast, consider the consumption of an alternative food source, such as four whole eggs. Protein and dietary fat do not provoke the same sharp insulin response as refined carbohydrates and sugars. Instead of storing the energy away as fat, the body efficiently burns the available energy to meet its metabolic demands, leaving the individual feeling satiated and satisfied.
Challenging the long-held dietary equivalence that treats all calories the same, Dr. Fung poses a straightforward rhetorical question: “Why do we pretend that 500 calories of cookies are the same as 500 calories of broccoli? They’re completely different.”
Ultimately, the hormonal response dictated by the specific type of food consumed determines whether the body decides to store fat or burn it for fuel. This hormonal reality explains why decades of strict calorie counting alone have consistently failed to provide a lasting solution for the global obesity epidemic.
The Real Culprit: Too Much Insulin
Building upon the failure of the calorie model, Dr. Fung identifies the root cause of both modern obesity and type 2 diabetes as hyperinsulinemia—a condition characterized by chronically elevated insulin levels in the bloodstream.
Insulin is a naturally occurring and essential hormone produced by the pancreas, playing a vital role in regulating nutrient storage and cellular energy. However, when circulating levels of insulin remain persistently high over long periods, it creates significant physiological dysfunction. When insulin is elevated, the body is locked into a fat-storage mode. Conversely, when insulin levels are low, the body is able to access and burn stored fat for energy.
A major turning point in public health occurred starting in the 1970s, when official dietary guidelines were introduced that encouraged populations to significantly increase their consumption of carbohydrates while drastically reducing their intake of dietary fats. The unintended consequence of this massive dietary shift was a chronic, population-wide elevation in insulin levels.
“When you’re eating a lot of carbohydrates, your insulin is going to go way up,” Dr. Fung explains, outlining the direct link between dietary composition and hormonal response. “And that’s why if you’re spiking insulin, you’re basically telling your body to please store more fat.”
This sweeping dietary transformation did far more than simply drive widespread weight gain across industrialized nations. It also catalyzed sharp increases in the prevalence of type 2 diabetes, cardiovascular disease, and metabolic syndrome, leaving public health experts to reexamine the foundational dietary advice that guided generations.
