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Diet & Nutrition


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Is “a calorie a calorie,” or will 

eating certain foods help me to lose weight?

— Sarah M., Syracuse, NY

Calories are dead. 

Did I get your attention? I thought so.

OK, I lied. Calories aren’t completely dead, but the belief that they are the main cause of weight gain is quickly approaching its sell-by date. Calories still matter—but they are no longer the star of the weight-loss show. Emerging research suggests that there are many other factors that affect weight gain and weight loss, and these factors are far more powerful than previously appreciated.

The Role of Hormones

Let’s start with hormones. Several hormones play important roles in fat storage, fat burning, and appetite, while others control such things as metabolic rate. In fact, one of the great shifts in thinking among cutting-edge health professionals has been a greater appreciation of the role hormones play in weight gain, and a greater appreciation of the hormonal effect of food.

The best-known example of a hormone with a direct impact on fat storage is insulin. Insulin, a hormone secreted by the pancreas, has many jobs in the body, but primary among them is that it acts as a kind of Sherpa for sugar in the bloodstream, escorting it out of the blood and into the muscle cells where it can be burned for energy. Insulin also escorts amino acids into the muscle cells, which is great if you’re working out heavily and trying to build muscle. But insulin is more likely to cause you to store fat.

Here’s how it works. When you eat food—most any food (with an exception we’ll discuss in a moment)—your blood sugar goes up. “High glycemic” foods (e.g., sugar, soda, white bread) make it go up higher and stay up longer.

When your blood sugar goes up, the pancreas jumps into action and secretes a squirt of insulin. Insulin’s job is to shepherd all that extra sugar out of the bloodstream—where high levels can do some serious damage—and into the muscle cells that, under ordinary circumstances, would be delighted to have it.

What are ordinary circumstances? Well, the circumstances that homo sapiens have found themselves in for the vast majority of the hundred thousand years or so we’ve been on the planet, at least up to the invention of agriculture. We had to move around a lot, hunt, fish, gather our food, and often travel long distances every day just in order to survive. No wonder the muscle cells were delighted to have any sugar that wound up in our bloodstream—they needed that sugar for fuel, since they had an awful lot of work to do!

Now? Not so much. See, it’s not just sugar that raises your blood sugar, it’s foods that convert to sugar quicker than you can pull out your smartphone and order Uber. These are the foods we’ve been told are healthy for the last few decades—cereals, pasta, rice, grains, low-fat cookies and crackers, potatoes, orange juice, and all the rest of the staples of the standard American diet. The pancreas goes on full alert—“This guy just ate 10 ding-dongs”—and starts secreting a ton of insulin.

But there’s a problem. For many people, the only “work” they ask the muscles to do on most days is a few hours of keyboard stroking, a trip back home to the couch, and an evening in which the only exercise they’ll be getting is pushing a button on the remote control. Insulin goes tapping on the doors of the muscle cells offering all that sugar that was just eaten, but the muscle cells aren’t interested. “What do we need that stuff for?” they ask. “Take it to someone who wants it!”

Over time, the muscle cells become resistant to the effects of insulin, a condition not surprisingly known as insulin resistance. They won’t open their doors. So guess where insulin takes its sugar payload?

Yup. To the fat cells. Which are all too happy to welcome it in. Eventually, in many cases, even the fat cells can’t absorb much more sugar. Then you’re in the unenviable position of having high blood sugar and high insulin levels in your bloodstream, the perfect storm for metabolic syndrome, diabetes, and obesity.

All Foods Are Not Created Equal

There’s an important take-away from this. All food does not raise blood sugar equally. “Low glycemic” foods—like, for example, virtually every vegetable on the planet—have a much less pronounced effect on blood sugar, and, consequently, on insulin. Many of them barely raise the blood sugar needle. Protein raises blood sugar—but not nearly as much as carbohydrates in general, and not a fraction as much as processed carbohydrates, which are the absolute worst offenders.

Guess what doesn’t raise blood sugar? Fat. Yes, the very macronutrient we’ve been warned away from during 40 years of bad dietary advice actually turns out to have the least effect on our fat-storing hormone, while the foods we’ve been told to consume the most of—complex carbohydrates like cereal, pasta, and rice—have the biggest effect. Starting to see the irony? Now you know why it’s so hard to lose weight on a low-fat diet!

Check Your Leptin Levels

Insulin has a central role in weight gain, but it’s not the only hormonal player. Leptin is a hormone that sends a message to the brain when you’re full. When researchers in the ’90s first discovered that obese mice have very low levels of leptin, they thought they had discovered the holy grail of weight loss. Obese people—like the obese mice—must be leptin-deficient, they reasoned. Drug companies began licking their chops at the thought of producing a pharmaceutical version of leptin that would cause people to drop weight.

Except that it didn’t. Researchers quickly discovered that obese people actually have plenty of leptin. The problem is that it doesn’t get into their brain cells, so it can’t deliver it’s “stop eating” message. This condition, known as leptin resistance, is like having a broken gas gauge on your car. You never know when the tank is full, so you keep filling it up at every gas station on the highway.

Like insulin resistance, some of the blame for leptin resistance goes to carbohydrates. High-carb diets raise triglycerides, and high triglyceride levels are one of the causes of leptin resistance. When you eat a low-carb diet, triglyceride levels tend to drop. Additionally, insulin levels tend to drop, and leptin activity begins to normalize—and you lose weight.

Other Factors

Weight gain often accompanies certain medications. The bloating and weight gain associated with long-term use of the steroid prednisone is a perfect example. Take two people on the identical diet and exercise program, give one of them prednisone for a couple of months, and see if you still believe calories are the only thing that determines weight gain. Clearly, some medicines can interfere with normal processing of calories. Some common drugs known for producing weight gain include Paxil, Depakote, Prozac, Zyprexa, and even some antihistamines.

Chemicals are another example. There’s been quite a bit of research in the last decade or so on chemicals in the environment known as obesogens because they literally trigger weight gain. Bruce Blumberg, a biology professor at the University of California, Irvine, coined the term “obesogen” in 2006 when he discovered that certain compounds predisposed laboratory mice to gain weight. “We’ve altered the physiology of these offspring, so even if they eat normal food, they get slightly fatter,” he wrote.

Some of these obesogens are common chemical pesticides found in food and water. Some are food additives like monosodium glutamate. Some chemicals and pesticides are known as hormonal or endocrine disrupters because they literally interfere with hormonal activity. These endocrine disrupters can affect weight, but they can also affect a lot more. The pesticide atrazine, for example, can actually turn male frogs into females.

Clearly, managing weight involves more than watching the number of calories we take in and expend every day. And appreciating the myriad of influences involved in gaining weight helps us increase our understanding of the disease that is obesity.

Jonny Bowden, PhD, CNS, aka “the Rogue Nutritionist,” is the author, with cardiologist Stephen Sinatra, MD, of The Great Cholesterol Myth. His program “Unleash Your Thin” can help you conquer cravings and food addictions and is available at Visit him at and follow him on Twitter @jonnybowden. Do you have a health question for Jonny? Send it to Write “Health Q&A” in the subject line.