A team of 17 internationally recognized scientists published a paper supported by more than 169 journal references, proposing that the current obesity epidemic is not caused just by taking in too many calories (Am J Clin Nutr, September 13, 2021). They believe that obesity is caused primarily by hormonal changes brought on by eating refined carbohydrates and sugar-added foods.
These foods cause a high rise in blood sugar that markedly:
• increases insulin secretion that makes you hungrier (N Engl J Med, 1971;285(8):443-9), and
• decreases glucagon secretion that functions to make you feel full, so you keep on eating (Trends Endocrinol Metab, 2018;29(5):289-99).
Insulin also causes changes in metabolism that signal fat cells to store more fat (Obesity, 2020;28(11):2098-106). These studies do not recommend restricting all carbohydrates, just those that cause high rises in blood sugar (Science, May 7. 2021).
What Are Unrefined and Refined Carbohydrates?
Unrefined carbohydrates are parts of plants that have not been stripped of their other outer coatings, ground up and otherwise changed before you eat them: whole fruits, vegetables, un-ground whole grains, beans, nuts and other seeds. Refined carbohydrates are plant parts that have had basic components removed or have been ground into flour: all extracted sugars, bakery products, pastas, most dry breakfast cereals and so forth. Fruits can contain a lot of sugar, but they are considered unrefined because they have soluble fiber and antioxidants that markedly reduce the rise in blood sugar when you eat them (Exp Ther Med, Aug, 2016;12(2): 1232–1242)..
You Need Carbohydrates
Carbohydrates are usually the main source of energy for our bodies to function, while protein provides amino acids to grow and repair our cells. Carbohydrates are sugars in singles and combinations of up to millions of sugars bound together. Humans can absorb only single sugars. Most unrefined carbohydrates contain many sugars bound together, and we lack the intestinal enzymes to break them down.
Most of the carbohydrates in vegetables, unground whole grains, beans, nuts and other seeds cannot be absorbed from the upper intestinal tract so they pass all the way to the colon where bacteria do have the enzymes to ferment them and break them down to short chain fatty acids or SCFAs (Proc Nutr Soc, 2015;74:13-22). These byproducts of fermentation by bacteria in the colon cause good bacteria to grow in the colon, which reduce inflammation that contributes to heart attacks, diabetes, cancer, and obesity (World J Gastroenterol, 2011;17(12):1519-1528). They also lower high blood pressure, high blood sugar, and high cholesterol.
Evidence Linking Refined Carbohydrates and Obesity
Overweight people who eat mostly whole foods rather than processed foods can lose weight without counting calories or restricting portion sizes:
• A study from Stanford showed that restricting processed foods, particularly added sugars and other refined carbohydrates, is more important for weight loss than going low-carb or low-fat (JAMA, Feb 18, 2018;319(7):667-679).
• A study from the University of Aberdeen showed that eating whole plants rather than refined plant foods, such as those made from flour or with added sugars, results in far more healthful intestinal bacteria than a diet with high protein or added amino acids (European Journal of Nutrition, February 20, 2018:1-12).
My Recommendations
• What you eat may be far more important than how much you eat.
• Obesity increases risk for heart attacks, cancers, diabetes and premature death.
• Counting calories or trying to limit portion sizes have been repeatedly shown to fail to control weight in the long run.
• Studies on colon bacteria are showing that eating lots of unrefined carbohydrates from plants and avoiding refined carbohydrates, such as sugar-added foods and drinks and foods made from flour, can help people lose weight and keep it off.
• I recommend eating plenty of vegetables, beans, whole grains, nuts and other seeds, and whole fruits.
Gabe Mirkin, M.D., is a sports medicine doctor and fitness guru. A practicing physician for more than 50 years and a radio talk show host for 25 years, Dr. Mirkin has run more than 40 marathons and is now a serious tandem bike rider with his wife, Diana. His website is http://drmirkin.com/. Click to read Gabe’s full bio.
This is a gross misrepresentation of the state of the art of the THEORY of the Carbohydrate-Insulin Model (CIM) vs the traditional EnergyBalance Model (EBM) of obesity. CIM is FAR from proven and remains controversial. The main study itself states “Rigorous research is needed to compare the validity of these 2 models, which have substantially different implications for obesity management, and to generate new models that best encompass the evidence.”
Part of the problem with the evidence behind the CIM is that the Glycemic Index of foods, the core variable here, is imprecise. Perhaps the most extensive data collection and research on GI is from the Univ of Sydney (glycemicindex.com, which includes useful a GI search function for specific food items). The experimental GI data for “unrefined” and “refined” carbs often overlaps significantly (unsurprising given that we have rather efficient enzymes in the mouth and gut (pancreatic amylase) to process most carbs). For example the observed GI of raw apples varies by over 50% and can be HIGHER than a (60 gm) Snickers bar!!! Further- the GI of foods can vary almost THREE FOLD depending upon how it is consumed (e.g. white bread eaten with varying amounts of almonds).
I am 100% supportive of eating healthy with vegetables, fruits, and non-red meat proteins, (and minimizing candy bars), but claiming that the quantity of food consumed has minimal relation to obesity is simply inconsistent with the available data. Portion control is still important. One cannot eat ‘healthy foods’ like a starved horse and expect lose weight.
The cited Ludwig ET al article is open access and should be linked: https://academic.oup.com/ajcn/advance-article/doi/10.1093/ajcn/nqab270/6369073.
It is a commentary, meaning is is really an editorial with no original data. I agree with John to a great extent. This paper is considered very controversial within the metabolism community. I do agree with avoiding refined sugar and over processed foods. There is also evidence that fructose is culprit because it is metabolized through different pathways than glucose. This is why high fructose corn syrup is particularly pernicious. Here is evidence artificial sweeteners are bad, too.
Eat a healthy, balanced diet, exercise and get a your sleep.
Great point Joe about artificial sweeteners in general. It has long troubled me that these have been pushed as a ‘healthy’ alternative (including by major health systems) with little evidence of even intermediate term benefit. And potential risks as you mention.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6313893/
The obesity ‘pandemic’ has been worldwide over the past decades, and has been associated in multiple regions/cultures with increased food energy intake (not just sugars, but fats as well) and decreases in fiber intake and physical activity. Difficult to prove the relative impact of each factor.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3257829/pdf/nihms336201.pdf
Personally- I try to avoid too much fructose due to GI intolerance. Surprising to me that more athletes are not aware of fructose GI intolerance issues.
As I already mentioned – any amount of biological/medical theories can’t override fundamental laws of physics.