Key Takeaways
- Obesity has traditionally been defined using Body Mass Index (BMI), but BMI alone may not accurately reflect metabolic health.
- In 1960, only 13% of Americans were considered obese, compared to 43% today using BMI standards.
- A new 2025 international expert panel proposes more precise criteria for obesity, incorporating body measurements and body fat percentage.
- Using these updated standards, nearly 69% of Americans may now qualify as obese.
- Weight loss from GLP-1 drugs does not necessarily eliminate obesity, and weight often returns after stopping treatment.
- Long-term metabolic health requires addressing insulin resistance, inflammation, and excess body fat, not just weight loss.
- Metabolic Engineering® aims to improve metabolism by activating AMPK, which helps burn fat, preserve lean mass, and reduce inflammation.
When the Supreme Court Justice Potter Stewart was asked how he defined hard-core pornography, he stated, “I know it when I see it”. The same might be true of obesity.
Obesity leads to early mortality. That is why the Metropolitan Life Insurance Company started compiling data on height, weight, and mortality in the 1940s to determine who was most likely to die, so they could adjust the cost of an individual’s life insurance policy and make money like any good bookie. These charts were based on height and weight. The ideal range indicated you were less likely to die. Above or below those ranges, your likelihood of dying was greater. Obviously, there were different tables for men and women. As time went on, the ideal body weight for longevity was further adjusted for frame size (usually based on the wrist circumference). Now the Metropolitan Life tables began to look like a computer printout sheet.
So, to make it simpler (and not to make it sound like the Metropolitan Death Tables), the concept of BMI was first introduced by Ancel Keys in 1972 because a single number could be applied equally to men and women, regardless of sex or body frame. The average BMI had remained relatively stable in the 1960s and 1970s (1) but started to increase in the late 1970s (2). By 1997, the obesity epidemic was spreading worldwide. The World Health Organization adopted the use of BMI to measure obesity, and soon afterward, the US government followed suit. The only trouble was that BMI levels had been rapidly increasing since 1980.
You are considered obese if your BMI is greater than 30. In 1960, about 13 percent of Americans would be considered obese, and that rate only slightly increased to 15 percent by 1980. Currently, 43 percent of Americans meet that criteria. That’s nearly a 300 percent increase in 45 years. Also, remember that the Metropolitan Life Insurance Company began publishing its tables because obesity was strongly associated with early mortality. The only reason Americans aren’t dying faster is that we have greater use of drugs to treat the problems created by obesity, even though the underlying issue (i.e., excess inflammatory fat) is out of control. However, what is decreasing is our healthspan, defined as the percentage of our lives spent in reasonable health. Currently, the US has the largest gap between healthspan and lifespan in the world (3).
Well, that is bad news. But what if reality is even worse than that?
How Is Obesity Defined Today?
In early 2025, an international expert panel decided on a new definition of obesity based on far more objective measurements (4). Any one of these four definitions would classify one as obese:
1. BMI greater than 40
2. BMI greater than 30 plus one elevated body measurement (like waist circumference, waist-to-hip ratio, or waist-to-height ratio)
3. BMI less than 30 plus two elevated body measurements
4. Excess body fat by dual-energy x-ray absorption (DEXA) or similar body fat measurements like underwater weighing. Using these measurements, obesity is defined as body fat greater than 25 percent for males and greater than 32 percent for females.
Using these new definitions of obesity, researchers then applied them to more than 300,000 subjects (5). What they found was that the average percentage of Americans who would be considered to be obese had jumped from 43 percent using the old BMI standard to 69 percent with the new standards. That’s a 60 percent increase in obesity using more objective standards. Yikes!
This only means that healthspan will continue to decrease in America even if everyone takes GLP-1 drugs. The reason is that the clinical studies indicate that the decrease in obesity is significantly less than the weight loss (6). Individuals taking the GLP-1 drugs for more than a year were still obese even by the old standards of obesity using only BMI measurements. According to old Metropolitan Life Tables, they are more likely to die than individuals with a lower percentage of body fat. More troubling is that once they stop taking GLP-1 drugs, the lost weight returns, and most likely as new body fat, thus potentially making them more obese than when they started.
What is the solution? I believe it lies in Metabolic Engineering®. This is a life-long dietary program to activate AMPK, the master regulator of your metabolism. Metabolic Engineering® allows you to burn stored body fat faster while maintaining your lean body mass, reduce inflammation, repair damaged tissue more rapidly, and slow your rate of aging. This also means your healthspan will increase.
FAQ
What is the medical definition of obesity?
Obesity has traditionally been defined using Body Mass Index (BMI). A BMI of 30 or higher is typically considered obese. However, newer medical definitions also consider body measurements and body fat percentage to more accurately identify metabolic risk.
Why isn’t BMI always accurate for measuring obesity?
BMI only considers height and weight, not body composition. Someone with a normal BMI may still have excess body fat or metabolic dysfunction, while a muscular individual may have a higher BMI but low body fat.
What are the new clinical criteria for obesity?
A 2025 international expert panel proposed broader criteria including:
- BMI greater than 40
- BMI greater than 30 plus an elevated body measurement (such as waist circumference)
- BMI under 30 plus two abnormal body measurements
- Excess body fat measured by scans such as DEXA
Using these criteria, obesity rates in the U.S. may be closer to 69% of adults.
Do GLP-1 weight-loss drugs eliminate obesity?
GLP-1 drugs can cause weight loss, but studies suggest that many patients remain obese even after treatment. In addition, weight often returns once the medication is discontinued.
How does metabolic health affect obesity?
Obesity is closely linked to insulin resistance, inflammation, and disrupted metabolism. Improving metabolic control—especially through diet and lifestyle—can help reduce excess body fat and improve long-term health outcomes.
References
1. Pray R, Riskin S. The History and Faults of the Body Mass Index and Where to Look Next: A Literature Review. Cureus. 2023;15:e48230. doi: 10.7759/cureus.48230.
2. Temple NJ. The Origins of the Obesity Epidemic in the USA-Lessons for Today. Nutrients. 2022;14:4253. doi: 10.3390/nu14204253.
3. Garmany A, Terzic A. Global Healthspan-Lifespan Gaps Among 183 World Health Organization Member States. JAMA Netw Open. 2024; 7:e2450241. doi:10.1001/jamanetworkopen.2024.50241
4. Rubino F et al. Definition and diagnostic criteria of clinical obesity. Lancet Diabetes Endocrinol. 2025;13:221-262. doi: 10.1016/S2213-8587(24)00316-4.
5. Fourman LT, et al. Implications of a New Obesity Definition Among the All of US Cohort. JAMA Netw Open. 2025; 8:e2537619. doi: 10.1001/jamanetworkopen.2025.37619.
6. Wilding JPH et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity. N Engl J Med. 2021; 384:989-1002. doi: 10.1056/NEJMoa2032183.
Key Takeaways:
- Allulose may naturally stimulate GLP-1 release, helping regulate appetite and fat metabolism without the need for injectable drugs.
- Early research suggests greater fat loss and less rebound weight gain compared to semaglutide in animal studies.
- Unlike traditional sugar, allulose is minimally absorbed and not counted as sugar, making it easier to incorporate into daily nutrition.
- Long-term success depends on body composition—not just weight, with diet (like the Zone Diet) helping preserve lean mass while reducing body fat.
What if there were a simple sugar that was more powerful than GLP-1 drugs in terms of fat loss? What if that simple sugar were already approved as a food additive so it could be added to food products like shakes, bars, oatmeal, and granola, making it realistic to take it for a lifetime?
And of course, what if that simple sugar were less expensive than any GLP-1 drug? If so, it could be a radical change in obesity treatment.
The first injectable GLP-1 drug (semaglutide) was introduced in 2017 for treating diabetes under the tradename Ozempic. The oral version of semaglutide for treating diabetes, under the trademark Rybelsus, was introduced in 2019, but you had to take it daily rather than a weekly injection. Not surprisingly, patient compliance was less than with a weekly injection.
Once injectable semaglutide was approved for weight loss in 2021 (under the trademark of Wegovy), TV advertising took off, and the world never looked back. A slightly altered form of Wegovy for oral use was approved in December 2025, but it has similar side effects to the injectable form[‘;;;.
Unfortunately, more than 50 percent of people who start GLP-1 drugs quit after one year most likely due to its side effects (1). Once you stop taking the GLP-1 drugs, the lost weight rapidly returns, and the metabolic benefits of the initial weight loss quickly erode (2).
Ok, what about that simple sugar? Its name is allulose. It has GRAS status as a food additive since 2012. What makes allulose unique is that it triggers the natural release of GLP-1 from the gut upon ingestion (3). Although 70% as sweet as sugar, allulose is rapidly excreted from the body, so the FDA doesn’t consider it sugar for labeling purposes. Its only drawback is that it can cause potential gut issues when consumed in high amounts.
The simple solution to that problem is to consume it in smaller amounts, three times a day, so you can enhance the release of GLP-1 from the gut each time you eat. The easiest way to do that is to incorporate it into food products that can be consumed at every meal.
Now what about the scientific data? A recent article compared oral semaglutide with allulose for weight loss in diet-induced obese mice (4). Although obese mice are not identical to obese humans, the results are highly suggestive. The appetite suppression in mice receiving allulose was greater, weight loss was greater, and the regain of lost weight after stopping supplementation was slower with allulose than with semaglutide.
A preliminary study in humans indicates that allulose has a dose-dependent effect on fat loss without any decrease in calorie intake (5). Although a direct comparison of high-dose oral allulose with injectable GLP-1 drugs remains to be done, the preliminary data suggests that adding allulose to your diet (or better yet including it in food products that are easily integrated into any diet) may provide a more natural alternative to achieving long-term weight loss than to use of chemically modified hormones (i.e., GLP-1 drugs) with their significant side effects.
However, it’s not just weight loss you want to achieve. Your primary goal if you want to live longer is to lose excess body fat, not just weight. A recent study suggested that your body fat percent is a better predictor of longevity than is your BMI (6).
Using GLP-1 drugs, there is a considerable loss of lean body mass along with the overall weight loss. The result is that your body fat percentage changes more slowly. Thus, your real goal is to lose excess fat and maintain lean body mass.
Published data demonstrate that when type 2 diabetics are put on the a dietary program that was consistent with the Zone diet in both the levels of calorie restriction (1,200 to 1,500 calories per day) and a macronutrient composition (40% carbohydrates, 30% protein, and 30% fat) the result was not only is there complete remission of their diabetes, but also an increase in their lean body mass (7).
So, what does this suggest for the future of obesity treatment? First, incorporating more allulose into your diet makes it far easier to achieve the real goal of changing your body composition to live longer than taking GLP-1 drugs. Second, incorporating allulose into a new generation of ZoneRx® Foods can make it easier to add it to your diet. Third, if you follow a Metabolic Engineering® dietary system using the Zone diet guidelines and incorporating ZoneRx® Foods as a source of allulose, coupled with adequate levels of omega-3 fatty acids and polyphenols, you will likely lose fat, gain lean body mass, and probably live longer.
- References
- 1. Rodriguez PJ, Zhang V, Gratzl S et al. Discontinuation and reinitiation of dual-labeled GLP-1 receptor agonists among US adults with overweight or obesity. JAMA Netw Open. 2025 Jan 2;8(1):e2457349. doi: 10.1001/jamanetworkopen.2024.57349.
- 2. Tzang CC, Wu PH, Luo CA et al. Metabolic rebound after GLP-1 receptor agonist discontinuation: a systematic review and meta-analysis. EClinicalMedicine. 2025 Nov 28;90:103680. doi: 10.1016/j.eclinm.2025.103680.
- 3. Iwasaki Y, Sendo M, Dezaki K et al. GLP-1 release and vagal afferent activation mediate the beneficial metabolic and chronotherapeutic effects of D-allulose. Nat Commun. 2018 Jan 9;9(1):113. doi: 10.1038/s41467-017-02488-y.
- 4. Rakhat Y, Banno S, Zhantleu D et al. D-Allulose reduces weight more persistently than oral semaglutide while both equally elevate grip strength in diet-induced obese mice. Nutrients. 2026 Feb 23;18(4):707. doi: 10.3390/nu18040707.
- 5. Han Y, Kwon EY, Yu MK et al. A preliminary study for evaluating the dose-dependent effect of d-Allulose for fat mass reduction in adult humans: A randomized, double-blind, placebo-controlled trial. Nutrients. 2018 Jan 31;10(2):160. doi: 10.3390/nu10020160.
- 6. Mainous AG, Yin L, Wu V et al. Body mass index vs. body fat percentage as a predictor of mortality in adults aged 20-49 years. Ann Fam Med. 2025 Jul 28;23(4):337-343. doi: 10.1370/afm. 240330.
- 7. Stentz FB, Lawson D, Tucker S et al. Decreased cardiovascular risk factors and inflammation with remission of type 2 diabetes in adults with obesity using a high protein diet: Randomized control trial. Obes Pillars. 2022 Dec 1;4:100047. doi: 10.1016/j.obpill.2022.100047.
This podcast covers these topics. Click to see more related podcasts:
What Is Obesity? BMI, Body Fat, and the New Medical Definition Explained
Barry Sears
Founder & President, Zone Labs
Read Time: 10 minutes
Table of Contents
Key Takeaways:
- Obesity has traditionally been defined using Body Mass Index (BMI), but BMI alone may not accurately reflect metabolic health.
- In 1960, only 13% of Americans were considered obese, compared to 43% today using BMI standards.
- A new 2025 international expert panel proposes more precise criteria for obesity, incorporating body measurements and body fat percentage.
- Using these updated standards, nearly 69% of Americans may now qualify as obese.
- Weight loss from GLP-1 drugs does not necessarily eliminate obesity, and weight often returns after stopping treatment.
- Long-term metabolic health requires addressing insulin resistance, inflammation, and excess body fat, not just weight loss.
- Metabolic Engineering® aims to improve metabolism by activating AMPK, which helps burn fat, preserve lean mass, and reduce inflammation.
When the Supreme Court Justice Potter Stewart was asked how he defined hard-core pornography, he stated, “I know it when I see it”. The same might be true of obesity.
Obesity leads to early mortality. That is why the Metropolitan Life Insurance Company started compiling data on height, weight, and mortality in the 1940s to determine who was most likely to die, so they could adjust the cost of an individual’s life insurance policy and make money like any good bookie. These charts were based on height and weight. The ideal range indicated you were less likely to die. Above or below those ranges, your likelihood of dying was greater. Obviously, there were different tables for men and women. As time went on, the ideal body weight for longevity was further adjusted for frame size (usually based on the wrist circumference). Now the Metropolitan Life tables began to look like a computer printout sheet.
So, to make it simpler (and not to make it sound like the Metropolitan Death Tables), the concept of BMI was first introduced by Ancel Keys in 1972 because a single number could be applied equally to men and women, regardless of sex or body frame. The average BMI had remained relatively stable in the 1960s and 1970s (1) but started to increase in the late 1970s (2). By 1997, the obesity epidemic was spreading worldwide. The World Health Organization adopted the use of BMI to measure obesity, and soon afterward, the US government followed suit. The only trouble was that BMI levels had been rapidly increasing since 1980.
You are considered obese if your BMI is greater than 30. In 1960, about 13 percent of Americans would be considered obese, and that rate only slightly increased to 15 percent by 1980. Currently, 43 percent of Americans meet that criteria. That’s nearly a 300 percent increase in 45 years. Also, remember that the Metropolitan Life Insurance Company began publishing its tables because obesity was strongly associated with early mortality. The only reason Americans aren’t dying faster is that we have greater use of drugs to treat the problems created by obesity, even though the underlying issue (i.e., excess inflammatory fat) is out of control. However, what is decreasing is our healthspan, defined as the percentage of our lives spent in reasonable health. Currently, the US has the largest gap between healthspan and lifespan in the world (3).
Well, that is bad news. But what if reality is even worse than that?
How Is Obesity Defined Today?
In early 2025, an international expert panel decided on a new definition of obesity based on far more objective measurements (4). Any one of these four definitions would classify one as obese:
1. BMI greater than 40
2. BMI greater than 30 plus one elevated body measurement (like waist circumference, waist-to-hip ratio, or waist-to-height ratio)
3. BMI less than 30 plus two elevated body measurements
4. Excess body fat by dual-energy x-ray absorption (DEXA) or similar body fat measurements like underwater weighing. Using these measurements, obesity is defined as body fat greater than 25 percent for males and greater than 32 percent for females.
Using these new definitions of obesity, researchers then applied them to more than 300,000 subjects (5). What they found was that the average percentage of Americans who would be considered to be obese had jumped from 43 percent using the old BMI standard to 69 percent with the new standards. That’s a 60 percent increase in obesity using more objective standards. Yikes!
This only means that healthspan will continue to decrease in America even if everyone takes GLP-1 drugs. The reason is that the clinical studies indicate that the decrease in obesity is significantly less than the weight loss (6). Individuals taking the GLP-1 drugs for more than a year were still obese even by the old standards of obesity using only BMI measurements. According to old Metropolitan Life Tables, they are more likely to die than individuals with a lower percentage of body fat. More troubling is that once they stop taking GLP-1 drugs, the lost weight returns, and most likely as new body fat, thus potentially making them more obese than when they started.
What is the solution? I believe it lies in Metabolic Engineering®. This is a life-long dietary program to activate AMPK, the master regulator of your metabolism. Metabolic Engineering® allows you to burn stored body fat faster while maintaining your lean body mass, reduce inflammation, repair damaged tissue more rapidly, and slow your rate of aging. This also means your healthspan will increase.
FAQ
What is the medical definition of obesity?
Obesity has traditionally been defined using Body Mass Index (BMI). A BMI of 30 or higher is typically considered obese. However, newer medical definitions also consider body measurements and body fat percentage to more accurately identify metabolic risk.
Why isn’t BMI always accurate for measuring obesity?
BMI only considers height and weight, not body composition. Someone with a normal BMI may still have excess body fat or metabolic dysfunction, while a muscular individual may have a higher BMI but low body fat.
What are the new clinical criteria for obesity?
A 2025 international expert panel proposed broader criteria including:
- BMI greater than 40
- BMI greater than 30 plus an elevated body measurement (such as waist circumference)
- BMI under 30 plus two abnormal body measurements
- Excess body fat measured by scans such as DEXA
Using these criteria, obesity rates in the U.S. may be closer to 69% of adults.
Do GLP-1 weight-loss drugs eliminate obesity?
GLP-1 drugs can cause weight loss, but studies suggest that many patients remain obese even after treatment. In addition, weight often returns once the medication is discontinued.
How does metabolic health affect obesity?
Obesity is closely linked to insulin resistance, inflammation, and disrupted metabolism. Improving metabolic control—especially through diet and lifestyle—can help reduce excess body fat and improve long-term health outcomes.
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References
-
Pray R, Riskin S. The History and Faults of the Body Mass Index and Where to Look Next: A Literature Review. Cureus. 2023;15:e48230. doi: 10.7759/cureus.48230.
-
Temple NJ. The Origins of the Obesity Epidemic in the USA-Lessons for Today. Nutrients. 2022;14:4253. doi: 10.3390/nu14204253.
-
Garmany A, Terzic A. Global Healthspan-Lifespan Gaps Among 183 World Health Organization Member States. JAMA Netw Open. 2024; 7:e2450241. doi:10.1001/jamanetworkopen.2024.50241
-
Rubino F et al. Definition and diagnostic criteria of clinical obesity. Lancet Diabetes Endocrinol. 2025;13:221-262. doi: 10.1016/S2213-8587(24)00316-4.
-
Fourman LT, et al. Implications of a New Obesity Definition Among the All of US Cohort. JAMA Netw Open. 2025; 8:e2537619. doi: 10.1001/jamanetworkopen.2025.37619.
-
Wilding JPH et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity. N Engl J Med. 2021; 384:989-1002. doi: 10.1056/NEJMoa2032183.
