The Delta | Blog

Online scientific presentations for sophisticated lay audiences are moving front and center in explaining the core arguments in debates about how we should eat. In Video Bookmarks, I’ll pass along notes and links to well-documented thought pieces on topics that provoke endless spin in the health media. The next few book marks are about calorie intake, the root causes of overweight and obesity, and carbohydrates in the diet.

In this video of a 2011 presentation at Ohio State University Medical Center, Gary Taubes tackles the persistence of outdated ideas about energy balance and carbohydrate consumption. Taubes, author of Why We Get Fat and Good Calories, Bad Calories, is a science journalist whose passion is exploring how theories get traction and how accepted theories are overthrown by newer, better evidence. His work on contemporary nutrition recommendations harnesses deep knowledge of the scientific and popular nutrition and weight loss literature.

He highlights why the scientific especially public health establishment is reluctant to let go of over-simplified calories-in-calories out models and the low-fat/high carbohydrate paradigm adopted in the 1970s and 1980s despite newer persuasive evidence. Highlights include his rapid take on why the Adkins diet and low carb approaches in general deserve careful attention.

Bookmark this for when you have time to relax into exploring these concepts in a lecture format (skip the first 5 minutes if you want to forgo the formal introductions). Provocative and carefully documented ideas make the investment well-worth it for gaining crucial new information.

K. Hartmann, MD, PhD

khartmann@thedelta.com

This blog is not intended to guide individual medical care or health decisions; it cannot substitute for professional consultation and guidance or supplant recommended treatments, prescriptions or plans of care.

 

Glucose is our primary fuel (other necessary nutrients like amino acids from protein are predominantly building blocks for cellular structures). Blood levels of glucose are controlled through multiple feedback loops to keep supplies within an expected and tolerable range for your body’s needs. The liver and muscles release glucose from glycogen stores when supplies are short because of demands like an extended time from the last meal or from exercise.

When blood glucose rises as a result of digesting and absorbing food, insulin helps direct glucose into cells. Like a key that fits into a receptor “lock” it opens the door for glucose to stream in. The degree and duration of the rise in blood glucose help determine the magnitude of the insulin response. More glucose means more insulin.

Insulin, produced by the pancreas, is the “hormone of abundance” – it encourages cells to take up available glucose and make use of it. In adipose (fat) cells, insulin signals the cells to take in glucose, increase production of fatty acids, and make more triglycerides for storage. In muscle, insulin improves glucose entry, prompts storage as glycogen for reserve fuel, and decreases breakdown of muscle proteins. In liver, insulin increases lipid production which makes its way to the bloodstream as well, and decreases glycogen breakdown.

The net effect when there is an excess of glucose, (more than we need to fuel and to keep glycogen storage depots full), is that insulin is working to tell fat cells to get fatter. What does that mean for food choices? Consider the figure below as an example.

A meal with a high glycemic load (for instance orange juice, a cinnamon role, and coffee with sugar) “spikes” blood sugar. In the example in red, the excess in blood sugar above needs for energy is more than double that of a meal of “slow” and “mixed” carbohydrates in purple like oatmeal with almonds, apple, and blueberries, skim milk, and coffee with sugar free creamer. (Compare the area in red vs purple above the need/spare line.)

This figure shows an instance in which total carbs, as indirectly measured by total area under the glucose level curve, are roughly equivalent but the metabolic effects would be starkly different. The “red” meal would result in fat storage unless you worked to elevate the “needs” line through high energy expenditure like that in high intensity interval training or running (not jogging). Energy needs blunt the curve – exercise removes the peak by using the glucose. The “purple” meal would likely, depending on individual metabolism, replete glycogen stores and prompt little fat storage. This illustrates why total calories or even total carbohydrates in the meals can be identical and the fat storing effect result from one eating pattern and not another. Indeed it is patterns of eating and not a single meal that lead to longer term effects on weight, body fat composition, and metabolism.

If you’re eager to experience* the low/slow carb effect and test whether it influences your weight loss or ease of weight maintenance, an easy step is to screen nutrition labels. Keep an eye on the sugars and total carbohydrates. By anecdote many see dramatic and sustained effects from eating only those carbs with no “sugars” which generally translates to unprocessed or whole grain foods. Multigrain breads and crackers, tempeh, whole oats, vegetables, nuts, soy, and beans fit this description (of course proteins and fats do not contain carbohydrate). A less severe but still demanding restriction is to keep sugars under 7 grams and total carbs under 20 grams per serving. If you know the content of your diet well and know this is a step in the right direction either of these can be an eye-opening experiment worth of a week or longer trial*. In a later blog we’ll talk about the totally-personalized experiment of using a blood glucose monitor to understand what really knocks your individual glucose metabolism for a loop.

K. Hartmann, MD, PhD

khartmann@thedelta.com

*Please make health decisions in personal consultation with a professional who understands your health and fitness profile. Acting on this advice could be harmful if you have certain forms of diabetes, take specific medications, or have other medical disorders.

Since all calories are not created equal (290 calorie bison burger ≠ 290 calorie doughnut), what does it make sense to focus on as you shape up your diet? If we consider it essential to know your total protein, fat, and carbohydrate intake goals, then honing in on the glycemic profile of the carbohydrates you eat is a strong second. Carbohydrates, whether in bean sprouts or an Almond Joy,  are converted to simpler sugars to fuel the body. Some carb sources, like Pixie Stix, fruit juice, or sugar in your coffee, which contain dextrose, fructose, and sucrose, require little or no digestion – they appear in the bloodstream quickly and are ready to use as fuel virtually immediately. Complex carbohydrates like those in whole grain bread, hummus, and black beans are converted more slowly.

This concept of “fast” and “slow” carbs is formalized by the glycemic index (GI) and glycemic load (GL). In a controlled research setting the index compares the blood sugar profile of healthy study participants consuming  50 grams of the carbohydrate being indexed to the blood sugar response of an equal amount of glucose over two hours after consumption. Glucose, the reference standard for the fastest carb has a GI value of 100. So a food that raises blood sugar half as much over the two hours has a GI of 50.

Lower and longer blood sugar response for the same number of grams of carbohydrate means lower insulin levels, less tendency to store excess as fat, and better control of hunger signals. Relatively few foods, just hundreds of the thousands of common foods we eat, have been formally tested for GI using the gold-standard method of “in vivo” testing in humans. At the high end of GI are baked potatoes at 80s to 90s and fruit roll ups, with a GI of 99.  (Yes, we’ve been feeding our toddlers nearly pure sugar.  In contrast, honey averages 55.)  White wheat flour bread comes in at 70; cranberry juice cocktail at 68, oatmeal, 58. White rice is 68 compared to brown rice at 55.

At the low end are apples and milk (most in high 20s to 30s for GI) ,  barley and cashews at 22, soybeans at 18. For convenience sake, and to allow for estimation rather than direct testing, foods are more often grouped into high GI (from estimated GI of 70 and above) medium (from 69 to 55) and low (55 or lower). The concept of glycemic load (GL) further refines the GI by taking into account typical portion size. For foods that are bulky and high in fiber we may not consume as much as is required to consume the same volume of food as the 50 gram test dose required for GI comparison.

Tables grouping foods by GI are available in pocket book form and in reference tables online to help classify your favorite foods and special indulgences.  Some resources are listed below. As a simple rule of thumb look at the nutrition label and pick foods with lower “sugar” grams as a proportion of the overall carbohydrate grams in the food.

K. Hartmann, MD, PhD

khartmann@thedelta.com

Resources:

Kay Foster-Powell, Susanna HA Holt and Janette C Brand-Miller. International table of glycemic index and glycemic load values : 2002, in American Journal of Clinical Nutrition, Vol. 76, No. 1, 5-56, 2002.

The Official Website of the Glycemic Index and GI Database from the international leaders in GI testing in Sydney Australia.

Glycemic Index and Glycemic Load for 100+ Foods from the Harvard Health Letter.