Just when you thought it was safe to go back in the kitchen, here we go again.
The Atkins diet empire is in bankruptcy. The trendy low-carb versions of your favorite foods are piled up in the clearance carts at the back of your grocery store. Those monster all-bacon breakfasts have quietly slid off the specials board at your local eateries, to be replaced once again by cheap piles of hash browns and eggs.
But if you thought you’d heard the last of the low-fat/low-carb diet debate, think again. There is some very exciting new research sure to bring it back to the fore, and finally—one hopes—in a meaningful way. It seems now that scientists have shown that the big variable in deciding which is better isn’t so much the fat or the carbs—it’s you!
Of course, some of us have been saying that for a while.
The low-fat vs. low-carb dietary debate has been raging since long before the good Dr. Atkins introduced his smash-hit diet plan, dripping with fats and oils. The phenomenon of marketing that accompanied his plan brought tremendous attention to a fairly extreme, carnivorous version of low-carb eating, and while it was effective for some, it was dangerously unhealthy for others.
And like other diet theories before it, it was no one-size-fits-all solution; though to be fair to the late Dr. Atkins, it really wasn’t intended to be.
That’s because people are not theoretical. Your body isn’t some anatomical embodiment of various average results of research studies proving one thing or another. General principles of weight management generally apply to the general population, and there are some fundamental truths that hold for pretty much everyone. But how those are expressed in any given individual, well, that’s subject to a lot of variables.
Frustrated and sincere people have been coming to us for years complaining of failure after failure with different diets that they say seem to be working for their friends, but just not for them. On top of the frustration of their diet failures, they’re demoralized because their concerns have been poo-pooed and doubted. But we’ve found over and over that they’re not sandbagging.
Your individual weight problem has to be treated individually, based on your fat, and your muscle and your body chemistry. This new study makes that case beautifully.
Less in, but less of what?
Supermarket tabloids notwithstanding, everyone understands that for weight loss to occur, there have to be fewer calories consumed than calories burned. But the ongoing debate tends to be about how we make up the calories we do consume, and whether there is any significantly superior way to compose a low-calorie diet for weight loss based on the proportions of the macronutrients: fat, carbohydrates and protein.
At the heart of the low-fat/low-carb debate lies a little-discussed matter of body chemistry: insulin sensitivity. Whole-body insulin sensitivity is a measure of your body’s naturally produced insulin to regulate your glucose uptake and metabolism. People who are insulin resistant have to produce more insulin than normal to do those jobs, because their bodies are not responsive at normal levels of insulin production.
Normally, you don’t just start out insulin resistant or wake up that way one morning. Bodies tend to become more and more insulin resistant over time with weight gain, but it’s a vicious cycle, because insulin resistance then makes it easier to gain weight, and so much harder to lose it. As you might suppose, insulin resistance is a red-flag precursor to the dangerous disease of diabetes, in which patients are so resistant that their bodies can’t churn out enough extra insulin no matter how they try, and they have to take supplemental insulin. Before it gets to that point, it’s not irreversible. Insulin sensitivity can be increased with weight loss and other health improvements that come from diet and exercise.
Some scientists have suspected that there’s a relationship between the degree of insulin sensitivity a person has and the way they would respond to different macronutrient proportions in low-calorie diets. And those of us who have been doing patient care have certainly been trying to encourage that suspicion. After seeing this proven out in the blood work of thousands of patients, it’s not really a mystery to us anymore. But a clinical caseload, no matter how vast, is not a controlled study and treating physicians are typically not in the business of research science.
But at last, some research scientists have produced such a study, and it shows just what we’ve seen with patients all along: what’s good for the goose isn’t always good for the gander, or even another goose.
High fat or high carb
The researchers took 21 obese, non-diabetic women, did their blood tests and divided them according to whether they were insulin sensitive or insulin resistant. Then they were randomly assigned to receive either a high-carb/low-fat diet, or a low-carb/high-fat diet. Both diets offered the same overall caloric content; only the macronutrient proportions were different. The HC/LF diet was 60 percent carbs, 20 percent fat and 20 percent protein, while the LC/HF diet was 40 percent carbs, 40 percent fat, and 20 percent protein.
The subjects were kept on the controlled diets for 16 weeks. They were tracked for changes in their body weight, overall insulin sensitivity, blood lipids (fats) and their resting energy expenditure, a measure of metabolism.
And take a look at how these numbers shook out. The normally insulin-sensitive women on the high-carb/low-fat diet lost about 13 percent of their initial body weight, whereas those on the low-carb/high-fat diet lost only about 7 percent of their initial body weight.
But among the insulin-resistant women, the inverse was true! Those on the low-carb/high-fat diet lost about 13 percent of their initia body weight, as compared with only about 8 percent lost by those on the high-carb/low-fat diet.
The differences were not explained by changes in their resting metabolic rate, activity level, or overall intake, which of course was the same for both groups. And the changes in overall insulin sensitivity during the course of the study corresponded with the degree of weight lost by the participants. Those who had been insulin resistant developed improved sensitivity.
It was a small study, but it was well-designed and with results this dramatic, it’s likely to stimulate the further investigation the researchers say should now be done. And if their findings are confirmed in additional, larger studies, it could have great implications for how we go about tailoring weight loss plans in the future.
For doctors—and even patients—who have long understood the need for individualized weight-loss treatment, we won’t necessarily say we told you so, but not because we weren’t trying.