February 2010 Issue
Lose Weight the High-Protein Weigh
By Diane Welland, MS, RD
Vol. 12 No. 2 P. 34
How effective is this eating plan for shedding pounds? Examine the evidence to determine whether a carefully constructed diet emphasizing lean protein sources is a good fit for your patients.
High-protein diets have come and gone for decades, their popularity rising and falling like waves in the ocean. Who hasn’t heard of The Zone, the Atkins diet, or Sugar Busters? With unbalanced meal plans that sometimes restrict entire food groups, these fad diets often fail to meet humans’ essential needs for vitamins, minerals, and fiber, but they do usually lead to weight loss.
Several studies comparing high-protein, low-carbohydrate diets with high-carbohydrate, low-protein diets found high-protein diets to be just as effective and sometimes even more effective than their high-carbohydrate counterparts when it comes to weight loss. The latest study, published in The Journal of Nutrition in March 2009, looked at how a moderately high-protein meal plan measured up to the USDA’s Food Guide Pyramid diet over a 12-month period. Although weight loss results were similar in both groups, the high-protein subjects lost more body fat and had better blood lipid profiles than the high-carbohydrate dieters, according to the journal article.
This study is just one of many in a growing body of scientific evidence suggesting that the right high-protein diet may be a tool worth using in the fight against obesity.
The Diet Defined
With the media touting so many high-protein diets, it’s hard to pin down exactly what is considered a high-protein diet. Dietary Reference Intakes recommend a wide range—anywhere from 10% to 35% protein based on total calories. Recommended Dietary Allowances (RDAs) are set at a minimum of 0.8 g/kg body weight, or about 0.4 g/lb, but most nutrition professionals should plan on about 1.2 to 1.4 g/kg. Which method should you use?
“Whenever you’re talking about weight loss, you should always base protein needs on body weight, not percentage of calories,” says Donald Layman, PhD, professor emeritus of nutrition at the University of Illinois. “Percentage of calories is very misleading. Drop your calories and protein can easily dip below minimum levels. Keep the amount of protein the same and it can be considered high protein on one diet and low protein on another, yet it’s still the same amount of protein.”
Layman, who categorizes his diets as moderate in protein, aims for intakes between 120 and 130 g/day, or about 1.4 to 1.5 g/kg body weight (nearly double the RDA). “The average American woman eats about 70 g of protein a day, a man around 90 g per day, so most people would consider this a high-protein diet,” says Layman.
The rest of the diet is balanced between carbohydrates and fats. “Most traditional high-protein diets run about 40% to 45% carbohydrates, 25% to 30% protein, and no more than 30% fat, which turns out to be a pretty achievable diet,” says Roberta Anding, MS, RD, LD, CDE, CSSD, an American Dietetic Association media spokesperson and the director of sports nutrition at Baylor College of Medicine in Houston. Some high-protein diets even go as high as 35% protein.
In addition to protein, Layman’s laboratory diets usually include five servings of vegetables, two to three servings of fruit, and three servings of complex carbohydrates.
Why do we need so much protein? In his commentary on adults’ protein needs published in Nutrition & Metabolism in March 2009, Layman cites research showing that increased protein intake can benefit patients with osteoporosis, type 2 diabetes, metabolic syndrome, heart disease, and sarcopenia, in addition to obesity. Furthermore, as we age, our ability to utilize protein efficiently decreases.
“If you asked the average consumer who needs more protein, a 16-year-old or a 65-year-old, most people would say the 16-year-old,” says Layman. “In reality, it’s the 65-year-old. They likely need fewer calories, but they need more high-quality, nutrient-dense protein (along with exercise and specifically resistance training) to prevent muscle wasting.”
And while conventional weight-loss teachings generally reduce calories across all macronutrients—protein, fat, and carbohydrates—Layman says weight loss itself raises protein needs. “Losing weight is a stress on the body,” he says, “and any stress will increase protein needs.”
What gives protein the edge over carbohydrates when it comes to weight loss? In a word: satiety. Protein has greater satiety than either carbohydrates or fat, making people feel fuller and more satisfied for a longer period of time. As a result, they are better able to control their appetite and eat less.1,2
“I deal with mainly morbidly obese clients, and you just can’t get that satiety on a high-carbohydrate diet. They’re always hungry,” says Anding. “On a high-protein diet, clients feel less hungry, so they’ll stay with it.”
Studies (such as the one published in The Journal of Nutrition in March 2009 and one published in the American Journal of Clinical Nutrition in July 2005) show that subjects who replace protein for carbohydrate eat anywhere from 200 to 400 kcal less per day than high-carbohydrate dieters and find it easier to self-regulate their intake.
Another way in which protein benefits weight control is via thermogenesis, or the amount of energy needed to digest, absorb, and metabolize nutrients. Because protein has a higher rate of thermogenesis than both carbohydrate and fat, it uses up more calories.1-3
But by far the biggest impact on metabolism and energy expenditure involves protein’s role in both muscle building and muscle maintenance. “You need at least 30 g of protein in one meal to stimulate muscle building,” says Layman. “That’s the minimum. On the other hand, anything over 50 g and you’re maxed out. Protein then just gets oxidized and there’s no muscle benefit. Just to give you an idea of how much that is, sirloin steak contains about 8 g of protein per ounce, so 6 oz would be all you would need per meal.”
Unfortunately, hitting that 30 to 50 g range at every meal can be a problem, particularly for adult Americans, who tend to eat almost all of their protein in a single meal: dinner.
“Since positive protein balance only lasts about three hours after ingestion, it’s important to eat enough protein throughout the day,” says Layman, “and that can be pretty challenging for most people.” Thanks to our penchant for high-carbohydrate foods such as pasta, it’s not surprising that lunch often falls short. Breakfast, however, is by far the poorest protein meal of the day. According to Layman, most Americans average only 10 g of protein for the morning meal. For dietitians, this means coming up with creative ways to incorporate items such as chicken, fish, meat, eggs, cheese, Greek yogurt, milk, or beans into breakfast foods.
Building lean muscle mass isn’t the only benefit of high-protein diets; eating this way also preserves lean body mass during weight loss.4 “During starvation, we break down about 50% lean tissue and 50% fat. If you lose weight using a high-carbohydrate diet similar to the Food Guide Pyramid, you’ll be breaking down about 35% lean tissue and 65% fat,” says Layman. “Now go on a high-protein diet, and our research shows lean tissue breakdown drops to 20% while fat breakdown increases to 80%. Add exercise to the mix, and protein breakdown drops even lower—below 10%.”
Anding, who also counsels NFL football players, has seen similar results. “We’ve done a pilot study looking at high-protein diets (1.8 to 2 g protein/kg body weight), weight loss, and body composition in three groups: walkers, walkers with Pilates classes, and walkers with Pilates classes and weight training,” says Anding. “Only the weight-training group hung on to their lean muscle.” In fact, high-intensity weight training “using the heaviest weights with meticulous form” along with a high-protein diet was the only type of regime that resulted in 0% loss of lean muscle tissue and optimum weight loss. “We call this our ‘retired’ NFL diet,” notes Anding.
Other new research points to an inverse relationship between protein intake and abdominal obesity, the worst type of fat there is. But to date, only a few studies have been conducted, so the jury is still out.5
What to Keep an Eye On
• Fat: Although research has shown high-protein diets produce positive effects on blood glucose and blood lipid levels by decreasing circulating insulin, reducing triglycerides, and raising HDL levels—there is minimal effect on LDL levels—it’s important to remember that even with an emphasis on lean protein, this type of diet is still higher in total fat, saturated fat, and cholesterol than lower protein, high-carbohydrate diets, and long-term effects remain unknown.4 Furthermore, keeping the diet lean can be a challenge, particularly for clients who like fatty meats.
• Red meat: High-protein diets tend to be heavy on red meat. Even though data are inconclusive, high intakes of both red meat and processed meats, particularly if cooked at high temperatures, have been linked to an increased risk of prostate cancer in men.6 Dietitians need to encourage and educate clients about other sources of lean protein, such as chicken, turkey, and fish.
• Calcium: Since high-protein diets are directly related to higher outputs of urinary calcium, researchers in the 1990s concluded that high protein intakes had an adverse effect on bone. We now know that’s not the case. If accompanied by adequate calcium (about three servings of low-fat dairy per day), high-protein diets can not only increase calcium uptake (absorbing as much as 25%) but also enhance bone health, preserving bone even during weight loss, according to a 2008 Journal of Nutrition study.
• Fatigue: While a high-protein diet can be effective for weight loss, it may not be an optimum diet for every client who is trying to lose weight. “I’ve seen some clients who cut out carbohydrates and their energy output goes way down,” says Jim White, a personal trainer and RD in Virginia Beach. “They just become very fatigued.” For those individuals, higher carbohydrate diets work best.
• Kidney function: Despite a long-held belief that high-protein diets strain the kidneys, increasing the chances of problems later in life, there is little clinical evidence supporting this claim. We do know, however, that in populations that already have renal disease (or an increased risk of developing renal problems, such as those with diabetes), a high-protein diet may not be appropriate.7
How Low Can Carbs Go?
Current research centers on moderate-protein diets, low in carbohydrate and moderate in fat. Dietitians can tailor these diets to mainstream consumers and monitor them in a private practice setting—not so with traditional high-protein diets similar to the original Atkins diet introduced in the 1970s.
“I sometimes use a high-protein diet we call the ‘Medical Atkins diet’ to treat morbidly obese adolescents we see in the clinic at Baylor,” says Anding, “but it’s only as a last resort after they’ve tried everything else. It’s also their last chance to avoid gastric bypass surgery.”
Found in many diet manuals as a protein-sparing fast, this high-protein diet generally sets protein at 2 g/kg body weight and carbohydrates at 0 to 20 g at most. Still, with each patient who follows the diet, Anding grapples with an ethical dilemma. “When you strip away fruits and vegetables, you’re opening up huge nutrient holes in the diet. And although blood lipid levels improve, we’re more than just our LDLs and triglyceride levels,” she notes. “Are we inducing proinflammatory aspects? At times I worry, ‘Am I creating a perfect storm?’”
But for these patients—teenagers, some of whom need to drop 200 lbs or more—getting the weight off fast is the priority, and high-protein diets work. Once the patient is on the diet, he or she is carefully monitored by an interdisciplinary team, including Anding, a physician, an exercise physiologist, an endocrinologist, and a psychologist. How long each patient is on the diet depends on his or her individual condition. “I’ve had patients on this type of diet for six months,” says Anding, “because they’re so hyperinsulinemic, ketosis isn’t a problem.”
But there are downsides. Lack of carbohydrates alters mood “in the wrong direction,” says Anding, and recent studies have shown disruptions in cognitive function.8,9 “It’s really a matter of using your own clinical judgment, based on your assessment,” she says.
When it comes to determining whether a client will benefit from a high-protein diet, there’s no one size fits all; it depends on the client. Anding recommends that dietitians assess all of the variables and then use their own clinical judgment. “My first choice would always be a moderate, low-glycemic carbohydrate diet (45% to 50%), but if that’s not working or the patient is insulin resistant, you have to try something else,” she says.
Anding recommends looking for two things when assessing patients for a higher protein diet (25% to 35% protein): a waist circumference of 35 inches or greater in women and 40 inches or greater in men and the appearance of hyperpigmented skin around the nape of the neck (ie, acanthosis nigricans). Both are a sign of insulin resistance, which may be a result of hyperinsulinemia and metabolic syndrome.
“As dietitians, we’re trained to assess clients and then make clinical and dietary judgments based on this assessment,” says Anding. “But as the population changes, our skills at assessing and making clinical judgments must change, too.”
— Diane Welland, MS, RD, is a dietitian and freelance writer based in Springfield, Va.
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9. D’Anci KE, Watts KL, Kanarek RB, Taylor HA. Low-carbohydrate weight-loss diets. Effect on cognition and mood. Appetite. 2009;52(1):96-103.