High-Carb? High Protein? High-Fat? Is There a “Best” Way to Go for Weight Loss?



— By Larry Scherwitz and Deborah Kesten —

If you’ve ever lost weight and discovered how easy it is to gain it back, then you’ll appreciate how helpful it would be to know the best diet for maintaining weight loss. A key reason keeping weight off can be harder than losing it is this: after you lose weight, your body thinks it’s headed for a famine. So it instinctively conserves energy by slowing down your metabolism, the rate at which you burn energy (calories). This is understandable, because a low “burn rate” undoubtedly saved our ancient ancestors from starvation when, for millennia, they had to hunt and gather food—that may, or may not, be available. In other words, Mother Nature figured out what’s best for you: slow down your metabolism to up the odds of survival.


Which Diet “Amps Up” Your Burn Rate?

The what’s-the-best-diet-to-keep-weight-off conundrum recently emerged yet again when David S. Ludwig, MD, PhD, and colleagues at Children’s Hospital in Boston, published an intriguing study in the prestigious Journal of the American Medical Association.1 The question Ludwig posed is this: If you’ve been a successful loser—and have lost 10-15 percent of your body weight, what’s the best way to eat to ramp up your metabolism, and in turn, increase the odds of maintaining weight loss? To find out, he designed an eloquent study that took a close look at the number of calories that are burned, based on three different popular diets.

The 3 Diets

Because Ludwig wanted to find out if particular diets can increase metabolism after you’ve lost weight—which is when metabolism typically slows down, he started his study by having 21 overweight and obese young adult adults lose 10-15% of their body weight. To achieve this, all research participants (RPs) followed a diet consisting of 45-65% carbohydrates, 20-35% fat, and 10-35% protein diet, plus the guideline to avoid trans and saturated fat.

After losing weight, Ludwig launched the essence of the study. Over a four-week period, subjects consumed one of three diets, each of which contained the same number of calories. Before you look over the details of each diet, below, it’ll be helpful for you to know that glycemic index indicates the ability of different types of foods that contain carbohydrate to raise the blood glucose levels within 2 hours; while the glycemic load factors in the amount consumed of a specific food.

Here’s a breakdown of the diets in Ludwig’s study:

Very high-carbohydrate


Very high-carbohydrate (60% of calories)

Low-fat (20% calories from fat)

Low-protein (20% of calories)

High-glycemic load


Very low-carbohydrate

Very high-fat

Low-carbohydrate (10% of calories)

Very high-fat (60% of calories)

High-protein (30% of calories)

Low-glycemic load




Carbohydrates (40% of calories)

High-fat (40% of calories)

Low-protein (20% of calories)

Moderate glycemic load


Back to Ludwig’s question: Did any of the three popular diets bring the body’s burn rate back to the subjects’ pre-diet metabolism? No, they didn’t. But he did discover that the different diets did, indeed, have different burn rates: the very low-carb/very high-fat diet burned the most calories each day, followed by the low-glycemic/high-fat diet; while the very high-carb/low fat diet had the lowest burn rate.

Getting It Wrong

Do these findings tell us you’re more likely to attain and maintain weight loss with the very high-carb/low-fat diet? Not necessarily. Ludwig designed his study to measure burn rate only. And his study did, indeed, reveal that different diets produce different burn rates. But it only suggests a small metabolic advantage that may or may not exist. It didn’t shed light on whether any of the diets are better than another for weight loss.

Still, Ludwig’s study ignited a firestorm of inaccurate interpretations and conclusions. Media and advocates of a high-fat/high-protein/low-carb diet lauded Ludwig’s finding as the solution to losing weight and keeping it off. This is a dangerous and unsupported conclusion, because Ludwig’s very low-carb/very high-fat diet raised cortisol levels, a hormonal measure of stress. This matters a lot to you and your weight, because high cortisol levels promote body fat, in part by raising insulin resistance, a condition in which circulating blood glucose levels remain high. Add an increase in C-reactive protein (CRP), a measure of chronic inflammation that also resulted from the high-fat/high-protein diet, and you have a formula for increased risk of heart disease, diabetes, some cancers, weight gain, and more.


The Case for Carbs (and Not Fat)

In his blog about Ludwig’s study, neurobiologist Dr. Stephan Guyenet astutely points out research findings about carbohydrates and fat most media ignored:

  • “The carb:fat ratio,” says Guyenet, “has little or no detectable impact on energy expenditure in people who are not trying to lose weight.”2
  • At least three studies show the carbohydrate:fat ratio has little or no detectable effect if you are trying to lose weight.5,6
  • When you overeat—that is, when you consume more calories than you burn—the carbohydrates in your diet increase metabolism more than fat!3,4 This means that foods high in carbohydrates amp up your metabolism more effectively than high-fat fare. In contrast, if the extra energy you consume is from a high-fat diet, more is stored as body fat.

What does all this mean to you? Carbs may curtail weight gain better than a high-fat diet. A plethora of other studies concur. For instance, when scientists overfed rats with both high-carb and high-fat food, they found that fewer excess calories from carbs are stored as body fat (75-85%) when compared to excess calories from dietary fat (90-95%).3

Want more evidence about the carb vs. fat debacle? If you overeat a high-fat, high-carbohydrate diet, and, at the same time, you stop exercising (at least temporarily), the excess dietary fat you consume will pack on more pounds than the carbohydrates in your diet. Why? Carbohydrates have a better burn rate than dietary fat in food, meaning, it takes more calories for you to metabolize carbohydrates than fat.

Such studies tell us that carbs aren’t the evil put-on-the-pounds villain; and that eliminating carbs from your diet—and going high-fat/high protein instead, isn’t the magic potion for weight loss success.

Which leads to this question: What accurate conclusions can we draw from Ludwig’s study?

In Search of the Magic Potion

If you sort through all the media commotion and confusion, this take-home message emerges:  There may be a way to eat after losing weight to increase your metabolic rate. And this slight increase might give you a bit of an edge in making weight loss last.

But because the balance of carbohydrates, fat, and protein in Ludwig’s diets are extreme, it is unrealistic and unhealthy to turn to any of the diets in his study as a way to attain or maintain weight loss.

Let’s see if we can tease out the weight-loss potion we’re seeking—and get it right this time.

Get fresh-food savvy. Fresh, unprocessed, whole foods (fruits, veggies, grains, beans and peas, especially) are the way to go for weight loss. This is because most whole grains (such as oats, barley, buckwheat, brown rice, quinoa, and so on)—with the germ, fiber, and other nutrients intact in the kernel—tend to be low-glycemic. But tamper with the whole grain kernel or fresh fruit, and change its original form, and you’re asking for weight-gain trouble. Why? Glycemic index skyrockets if, for example, you consume instant oatmeal instead of whole (rolled) oat flakes, white rice instead of brown rice, or grapes that have been hydrated so they’re now super-sweet raisins.

The key guideline is this: Get fresh as often as possible, but don’t overeat grains—whether whole or processed. A diet that’s too high in carbohydrate-dense grains is a diet that’s also high in calories—the key contributor to weight gain.

Go low. A low-glycemic way of eating may be the most healthful and helpful diet for losing weight and keeping it off. You don’t have to be a scientist to know how to “go low.” Simply choose fresh, whole fruits; whole vegetables; whole, unprocessed grains; and legumes (beans and peas) as your most-of-the-time way of eating; with lesser amounts of lean and low-fat fish, poultry, meat, or dairy.

What’s relevant to your waistline is this: Anytime grains are processed—with the germ and fiber removed—the glycemic index doubles, going from low to high. This means that if a high-glycemic diet is your most-of-the-time way of eating, you’re increasing the odds of gaining weight and becoming obese. If you’re gluten-sensitive or intolerant, choose gluten-free or low-gluten grains.<

Get balanced. Ludwig and his team took the low-carb, low-fat diets to extremes so they could better discern differences burn rate, if any. He never intended his study to be used by health professionals or the public to adopt impractical, extreme, experimental dietary designs. In fact, he emphasizes a healthy balance of carbs, fat, and protein in your daily diet. Here’s a general guideline.

Carbohydrates: 45 – 65% (average 55%)
Fat: 20 – 35% of total calories (average 30%)
Protein: 10 – 35% (average 15%)

Increase or decrease the recommended ranges based on your personal health and preferences.

Court omega-3s. If your most-of-the-time way of eating includes lots of fast and processed food and beverages, it’s likely you’re one of the millions of Americans who are deficient in omega 3 fatty acids. And this matters to your waistline, because omega 3’s help you lose weight. To ramp up your intake, choose lots of fresh food, especially avocado, flax seed, nuts especially walnuts, and wild salmon and other deep-water cold fish (provided they are not caught in heavy- metal-polluted waters).

Overcome overeating. Overeating is overeating. Eat more calories than your body needs and it won’t discriminate whether the source is from too many carbs, fat, or protein. Even if you go low-fat and don’t consume a lot of calories from fat, you can put on pounds from too many carbs, even from too much protein.

Adding insult to injury, when you overeat, your body stores the extra energy (calories) as saturated fat. If the adipose tissue (which stores fat in your body) is already filled because you’re overweight or obese, then the excess fat finds other places in the body to lodge, such as between muscle fibers, in the liver, even the pancreas. The good news is that when you lose weight, this kind of health-harming fat is the first to go.

Avoid alien fats. The type of fat you typically consume is critical both to your weight and health. Above all, avoid trans fat, because this manmade fat harms health. And stay away from partially hydrogenated vegetable oils, because they’ve been exposed to high heat so they can remain on supermarket shelves for a long time without refrigeration. This changes the chemical composition of the oil—so much so that it becomes alien—and harmful—to the body. Even frying foods in vegetable oil creates a certain amount of trans fatty acids.

Way to Go for Weight Loss?

Low-glycemic. Fresh food. Whole grains. Omega 3s. Balanced nutrients. These ingredients have been available to you for millennia. They still are. And they’re still the smartest steps you can take to attain and maintain weight loss. So, too, is this time-tested advice: stop overeating (see our research and Successful Loser Series for more about this) and overloading on processed carbs (cake, cookies, chips, soft drinks, etc.).

Add regular physical activity, adequate sleep (7 hours), and stress reduction to the way-to-go-for-weight-loss formula and you have the time-tested magic potion you’re seeking to increase the rate at which you burn calories…and make weight loss last. These are far more effective strategies for losing weight and keeping it off than focusing on any one macronutrient (carbs, fat, protein) that may or may not have a small metabolic advantage.


  1. Ebbeling C, Swain J, Feldman h, Wong W, Hachery D, Garcia-Lago E, Ludwig D. Effects of dietary composition on energy expenditure during weight-loss maintenance. JAMA 2012;307: 2627-2634, PMID
  2. 2. Hill JO, Peters JC, Reed GW, Schlundt DG, Sharp T, Greene HL. Nutrient balance in humans: Effects of diet composition.The American Journal of Clnical Nutrition 1991;54: 10-17, PMID 2058571
  3. Horton TJ, Drougas H, Brachey A, Reed GW, Peters JC, Hill JO. Fat and carbohydrate overfeeding in humans: Different effects on energy storage.The American Journal of Clinical Nutrition 1995;62: 19-29, PMD 7598063
  4. Lammert O, Grunnet N, Faber P, Bjornsbo KS, Dich J, Larsen LO, Neese RA, Hellerstein MK, Quistorff B. Effects of isoenergic overfeeding of either carbohydrate or fat in young men. The British Journal of Nutrition 2000;84: 233-245, PMID 11029975
  5. Veldhorst MA, Westerterp KR, van Vught AJ, Westerterp-Plantenga MS. Presence or absence of carbohydrates and the proportion of fat in a high-protein diet affect appetite suppression but not energy expenditure in normal-weight human subjects fed in energy balance. The British Journal of Nutrition 2010;104: 1395-1405, PMID 20565999
  6. Yang MU, Van Itallie TB. Composition of weight lost during short-term weight reduction. Metabolic responses of obese subjects to starvation and low-calorie ketogenic and nonketogenic diets. The Journal of Clinical Investigation 1976;58:722-730, PMID 95639

Next post:

Think outside the diet to make weight loss last with “Study Uncovers 6 Ancient Healing Secrets of Food: Do they weigh In with weight loss?” posted on our NewView blog.

You’ll get plenty of clarity about what’s true and useful—or not—by keeping up with nutritionist Deborah Kesten, MPH, and research scientist Larry Scherwitz, PhD, the writers of this post, by following them on Twitter, liking them on Facebook, or sending us an email.

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