Food Processing and Obesity

So what happened? It is said that obesity is an interaction between genes and the environment. Well, our genes haven’t changed in the last 30 years, but the environment sure has. We all eat more, and exercise less. This isn’t news. But what is news is that our energy intake (what we eat and drink) and expenditure (what we use in everyday living – including normal activity and sports/exercise) are biochemically determined. So what in the environment changed our biochemistry?

To understand this dilemma, you have to understand a little biochemistry, but I’ll explain as simply as possible. The hypothalamus (the brain region which regulates hormones and energy balance) normally receives a signal from your fat cells (adipocytes) called leptin. Leptin is the fat cell hormone that tells your hypothalamus that you have enough energy stored in order to burn energy at a normal rate. Leptin levels can be too low (leptin deficiency, due to dieting or starvation) or too high (leptin resistance, if something blocks the leptin hormone from acting on those brain cells). In either case, the brain can’t see the leptin signal, and so the brain interprets it as a state of starvation. In this “starvation response”, two things happen: 1) the sympathetic nervous system (which controls your heart rate, blood pressure, and muscle metabolism) slows energy expenditure in order to conserve energy (which makes you feel bad), and 2) the vagus nerve (which controls your stomach, intestine, and pancreas) directs the body to store more energy as fat. Both of these “starvation responses” work to bring your leptin level higher. Obese people have high leptin levels, and therefore they are leptin resistant.

What blocks leptin signaling in obese people? Research over the past ten years suggests the following: leptin transport from fat cells to the brain is prevented by high triglyceride levels in the blood, and leptin release from fat cells is prevented by high insulin levels in the blood. This phenomenon is a normal response under some circumstances, such as the temporary blockage of leptin to promote weight gain during puberty and pregnancy, and is essential for reproduction and the survival of the species. But at other times, this phenomenon becomes a problem, as it causes the “starvation response” at a higher weight instead of a normal response at a lower weight. In addition, leptin resistance also fosters continued reward of food, which makes you eat more. These are the cardinal features of the obesity epidemic.

So, in order to prevent or treat obesity, we have to get the triglycerides and the insulin down. But what caused them to go up? This is where food processing affected our biochemistry directly. I can sum up the downside of food processing into two basic concepts.

1. Sugar. Dietary sugar is either sucrose (cane or beet sugar, composed of 50% glucose and 50% fructose) or high-fructose corn syrup (HFCS, composed of 45% glucose and 55% fructose). For lay purposes, both sugar sources are equivalent. Both are equally bad. It’s the fructose that is the problem. Fructose is what makes sugar sweet. But due to its unusual biochemical properties, fructose has been shown to increase the liver’s production of triglycerides, induces liver insulin resistance (making your liver sick), and drives your insulin levels up. All of this contributes to the phenomenon of leptin resistance, driving the obesity epidemic.

   Fructose has been added to most processed foods. Look at the food labels. The food industry says fructose improves palatability, is a better browning agent, and holds onto water, keeping things moist. But, a more sinister reason it’s added to processed food is that it makes you eat more! Soda, juice, and sports drinks are merely fructose delivery vehicles.

   Water is the perfect beverage; it has everything you need, and nothing you don’t.

   Two simple rules:

   1. If it’s a liquid, look at the calories. 6 or more, leave at the store! Milk is the only exception.
   2. If it’s a solid, look for the sugar in the ingredients. If any form of sugar is one of the first three ingredients, it’s a dessert!

2. Fiber. Fiber is the antidote to sugar. I like to tell my patients, “When God made the poison, he packaged it with the antidote”. Wherever there is sugar in nature, there is way more fiber. Sugar cane is a very fibrous plant that’s almost impossible to chew. Fruit has much more fiber than fructose.

   Fiber slows sugar absorption from the gut into the bloodstream. This gives the liver a chance to process the fructose, so the triglyceride levels in the blood are lower and the insulin rise is lower. Fiber also moves food through the gut faster. This leads to faster satiety (feeling full), which reduces the number of second portions. Unfortunately, fiber doesn’t freeze well – the ice crystals affect the molecular structure and it becomes mushy when it thaws. The food industry avoids this by removing fiber, to allow for freezing and increase the shelf life. So “fast food” is “fiberless food”, which makes it doubly bad.

   The answer here is: Eat your carbohydrate with fiber.

   Two simple rules:

   1. If it’s a solid, look for 3 gm of fiber or more.
   2. Eat the fruit, don’t drink the juice!

   But be careful, adding cereal fiber to processed food doesn’t do the job. The fiber must cover the starch or sugar molecules (i.e., whole grains) as it does with food that comes out of the ground, to reduce the rate of the sugar absorption in the gut.

So one big way to fight obesity is to fight food processing. We need to eat the way our ancestors did. We need to eat whole grains, fruits and vegetables, and a lot less sugar. And we need to relearn to cook. Eating this way often costs more, because the shelf life of such foods is much shorter. And with our current economic downturn, there is a premium for cheap food (since 2008, only two stocks are up: Wal-Mart and McDonalds). But for America to win the battle of obesity, we need to undo the damage that the food industry has done to us.