Overweight people who eat mostly whole foods rather than processed foods can lose weight without counting calories or restricting portion sizes.
• A new 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). This study had 609 overweight people, 18 to 50 years old (mean age 40), attend classes on healthful eating for weight loss for a year. They were divided into two groups — low-carb or low-fat. Both were told to eat lots of vegetables and other whole foods, and to avoid processed foods as much as possible, particularly those made from flour or with added sugars. The only differences were that the low-fat group was told to select plenty of healthful carbs such as quinoa, barley, steel-cut oats, lentils, beans and fresh fruits, while the low-carb group members were trained to choose a variety of healthful fatty foods such as avocados, nuts, nut butters, salmon, olive oil and hard cheeses. They made no effort to count calories or portion sizes.
Both groups lost about the same amount of weight, an average of 13 pounds in the year. Both groups also showed the same improvements in other markers of health, such as blood pressure, blood sugar levels and waist size. The researchers were particularly surprised to find that the people with high insulin blood levels did not do any better on the low-carb diet than on the low-fat diet. This study effectively demonstrates that overweight people can lose weight if they follow a healthful diet based on whole foods and restrict refined carbohydrates and other processed foods.
• Another new study, from the University of Aberdeen in Scotland, 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). The soluble fiber in unrefined carbohydrates is fermented by bacteria in the colon into healthful breakdown products that have been shown in other studies to help control weight and promote good health.
Eighteen overweight men ate a high-calorie diet, followed by 10 days on each of the following low-calorie diets:
• normal protein (15 percent of energy from protein and 55 percent from carbohydrate),
• normal protein with added free amino acids (40 percent from carbohydrate), or
• high protein (30 percent from protein, 40 percent from carbohydrate).
The carbohydrate diet without extra protein produced weight loss and large amounts of the healthful breakdown products of soluble fiber (butyrates and ferulic acid breakdown products from chlorogenic acid). On the other hand, the diets with added free amino acids and high protein produced much lower levels of these healthful results of carbohydrate fermentation.
How Some Colon Bacteria Can Help to Control Weight and Prevent Disease
Carbohydrates are a main source of energy for our bodies to function, while protein provides amino acids to grow and repair our cells. Taking in too much refined carbohydrates, particularly sugars, provides more energy than you need, so they are converted in your body to fat to increase your risk for becoming overweight.
Carbohydrates are sugars in singles and combinations of up to millions of sugars bound together. Humans can absorb only single sugars, not even two sugars bound together. Because they lack the intestinal enzymes to break down soluble fiber, resistant starches and non-starch polysaccharides into single sugars, these unabsorbed carbohydrates pass all the way to the colon where bacteria do have the enzymes to ferment them to break them down to short chain fatty acids, propionate, acetate and butyrate (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 increases risk for heart attacks, obesity, diabetes and cancer (World J Gastroenterol, 2011;17(12):1519–1528).
Definitions of Unrefined and Refined Carbohydrates
Unrefined carbohydrates are plant foods that have not been changed before you eat them: whole fruits, vegetables, un-ground whole grains, beans, nuts and other seeds. Refined carbohydrates include plant parts that have had basic components removed or been ground into flour: all extracted sugars, bakery products, pastas, most dry breakfast cereals and so forth. See Ultra-Processed Foods
The study from Aberdeen shows that dietary carbohydrates, not proteins, determine the amount of fermentation that bacteria cause in your colon. This helps to explain why eating added sugars and other refined carbohydrates such as bakery products, pastas and most dry breakfast cereals can make you fat, while eating unrefined carbohydrates in fruits, vegetables, nuts, seeds, un-ground whole grains, and beans can help to protect you from forming excess fat in your body.
• These two studies help us to understand why 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 eating tiny portions of food have been repeatedly shown to fail to control weight in the long run.
• Studies on colon bacteria are now 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.
• Eat plenty of vegetables, beans, whole grains, nuts and other seeds, and whole fruits.