This is part 2 in a series summarizing and reviewing “Always Hungry” by David Ludwig, MD, PhD. It may help to start reading these posts in sequence starting with part 1.
Chapter 3: The Science (pg 34-49)
Dr. Ludwig makes the case against calorie counting as the best way to lose weight. He acknowledges it is A way, but not the only, nor the best way. “The problems isn’t with our calorie-counting abilities or self-control, but rather the current understanding of the cause of — and cure for — obesity.” (pg 36) He cites systematic reviews (where many similar studies are viewed together) that look at the calorie counting model with and without exercise or behavior change therapy/counseling. He also notes that almost all of the weight participants may lose is regained.
This is due to biology. “When you eat fewer calories, the body becomes more efficient and burns fewer calories, even as your desire for extra calories heightens. … If we marshal a Herculean effort, stick to the diet, and stay active, metabolic rate will continue to fall, so we’ll need to cut calories even more drastically to keep losing weight.” (pg 37)
This maintaining of weight also works the other way too. In volunteers who are overfed naturally lose interest in food until they return to their “set point.” There is a great graphic on page 38 that shows this relationship. If body weight and energy expenditure are increased, hunger decreases so you are able to return to your set point. If the body weight is low, hunger is increased and energy expenditure decreased to allow for weight gain to set point. So, he reasons, the answer to weight loss must be in our fat cells themselves (not calorie manipulation).
“Adipose tissue is a highly specialized organ, cushioning vital organs, insulates against the cold, and as a “strategic calorie reserve to protect against starvation.” (pg 39)
At rest, one of every three calories is consumed by our brains. To our ancestors, having fat reserves meant the difference between life and death when famine, scarcity and crop failure came. A brain needs a constant supply of energy whether food is available or not.
What about calorie storage in our bodies?
Carbohydrate in the liver, 4 calories per gram
Protein, in muscles, 4 calories per gram
Fat, in adipose tissue, 9 calories per gram
Dr. Ludwig notes, fat cells are active and take in excess calories and release them as needed. He says they are part of chemical and neural messaging systems in metabolism and the immune system. Most notably, insulin.
Insulin is a hormone made in the pancreas. When you start eating, blood insulin levels rise and signal incoming macronutrients to enter body tissues (exiting the blood stream). Then, when blood insulin levels get low (a few hours after eating), stored fuels reenter the blood to be burned for energy. Research in human and animal models have shown that excess insulin leads to overeating and extra fat storage (even when the amount of calories consumed are controlled).
When we eat a meal with excess carbohydrate, especially refined carbs, the pancreas must produce even more insulin than normal to move the glucose into cells (and lower blood sugar). This causes even more glucose and fatty acids to enter fat cells (not available to the brain). The blood then runs out of calories faster making you more hungry sooner and since the fastest way to raise your blood sugar is carbs- that’s what you crave. Remember how important it is that the brain not run out of fuel? Being hungry is VERY stressful to your body because it’s literally trying not to die. Stress hormones (epinephrine and cortisol) enter the blood to access calories in the fat and liver. To conserve energy our metabolism slows down making weight loss difficult.
Let’s simplify a little (I have always liked lists). This is based on the graphic on page 45.
- Fat storage is increased by
- Processed carbohydrate increases insulin secretion
- Sleep deprivation
- Physical inactivity
- Other dietary factors
- This causes decreased calories in the bloodstream
- This increases hunger and food cravings (increased energy intake)
- Decreased metabolism and fatigue (decreased energy expenditure)
Dr. Ludwig explains an experiment he conducted with teenage boys. After eating one of three breakfasts (fast carb, slow carb or balance protein/carb) the boys were allowed to eat as much as they wanted for lunch. Those who ate the balanced meal consumed 650 calories less if they ate an omelet and fruit vs instant oatmeal (fast carb). The fast carb group also had a larger rise in adrenaline at four hours after breakfast causing symptoms of low blood sugar.
Another study (pg 48) showed that consuming high fructose corn syrup vs uncooked corn starch activates a brain region called the nucleus accumbens– the reward center. This suggests if one activates this region when on a low calorie diet, temptation would be too much to overcome.
“Hunger is hard enough to fight under any circumstances, but once the nucleus accumbens joins in, it’s all over.” pg 48
An interesting point that I hadn’t thought of this way before was that fat is not passive. It doesn’t just suck up extra calories, but interacts with the insulin and other messengers in the body.
I wonder how much other research exists surrounding how different carbohydrate sources are processed in the body. I know my body reacts differently to sugar in candy than it does to a breadstick.
I will finish chapter 3 in my next post.