After hours of sweaty stove-side work,
I had created a masterpiece: roasted red snapper on a bed of linguine draped with mango
salsa; sautéed spinach and potatoes on the side with a bowl of fresh strawberries for
dessert. But when my friend Scott arrived for dinner he wouldn't eat. He was trying a new
high-protein diet and couldn't eat carbohydrates. This diet, he hoped, would help him feel
more energetic and improve his athletic performance.
Baffled by news of Scott's seemingly illogical theory, I set out to learn a little more
about it. What I discovered is one of the greatest current controversies in nutrition
The Pros of High Protein
Since the late sixties, beginning with the work of Dr. Robert Atkins, alternative doctors
have suggested a protein-centric, low-carb diet as a means to lose weight and feel more
energized. This plan has been dismissed repeatedly as unsubstantiated fad by most in the
medical profession, but continues to find traction among athletes and dieters alike.
Whether it's Atkins' diets, Barry Sears' popular Zone diet, or Dr. Phil Maffetone's
40-30-30 (40% carbs, 30% protein, 30% fat), high protein diets are based on the premise
that carbohydrates induce weight gain through increased fat storage and perpetually
induced hunger. Carbs also lead to peaks and troughs in energy levels, as well as
increased production of insulin. Insulin helps the blood cells absorb glucose quickly,
causing a fast depletion of blood sugar levels. Insulin has also been associated with
increased risk of cancer and other diseases, protein proponents say.
"Elevated insulin combined with excess carbohydrate calories leads to increased
triglycerides, obesity, and production of pro-inflammatory eicosanoids. All three are
major factors for developing heart disease," Writes Zone advocate Dr. Paul
Without excessive carbohydrates, your body will turn to its fat stores for fuel, according
to this theory. Maffetone also claims a high protein, low carb diet will ease the mental
and physical fatigue commonly experienced after eating, as well as improve memory, reduce
intestinal gas, and alleviate depression. "By moderating carbohydrate intake to
control insulin production, you can increase your fat burning as an optimal and efficient
source of almost unlimited energy."
Carbo-Centrists Speak Out
But the research of protein advocates like Atkins or Maffetone isn't convincing mainstream
nutrition experts, who firmly believe that carbohydrates are the body's main source of
fuel, especially for active individuals.
"Unfortunately these claims rely on unpublished research or studies that have not
been peer reviewed or controlled, meaning they have little respect in the scientific
community," wrote Lisa Hark, Ph.D., RD, CDE in her article "The Reincarnation of
the High Protein Diet." Hark explains that the high protein theories are unfounded
mainly because your body converts all calories to glucose, to be stored as fat for energy,
regardless of whether those calories come from carbohydrates or protein. "It's your
overall calorie intake and not carbohydrates that cause fat to be stored. And besides,
foods that are high in protein, such as meats and cheeses, are also high in saturated fat,
which we now know will increase blood cholesterol levels if eaten in excess."
Dr. Amy Roberts, Coordinator of Sports Science at the Boulder Center for Sports Medicine
and the Sports Science and Asimba Nutrition Editor, concurs. If you see a big weight loss
over time, she says, it's because people have reduced their total calories. "A high
protein diet is not appropriate weight loss," she says. She notes that dieters need
to take care to find sufficient nutrients and not reduce their caloric intake to unhealthy
levels. She adds that much of the weight lost in a high protein diet is water. Also,
Roberts says, your body will only absorb a certain amount of protein, leaving the rest to
waste-and too much protein could lead to severe dehydration or kidney disease.
"And it's really silly to think that only food raises insulin levels," Roberts
adds. It is true that sugar leads to greater insulin production than protein does, (in
healthy adults) but only minimally, she says, and the risk associated with insulin is not
substantial. Roberts also points to other variables that promote insulin production,
including adrenaline and excitement, and adds that exercise is the best way to reduce
insulin levels, not dieting.
Most major health organizations, including the American Heart Association, the National
Institute of Health, the American Cancer Society, the Food and Drug Administration, and
the National Cholesterol Education Program endorse a carbohydrate-centric diet consisting
of roughly 30% fat, 10% protein, and 60% carbs. Roberts says athletes may need slightly
more proteins, but still suggests a similarly balanced breakdown: 20% protein, 65% carbs,
and 15% fat.
"I think the 40-30-30 is very unrealistic." says marathon runner, registered
nutritionist and Rocky Mountain Chapter of the American College of Sports Medicine board
member Cindy Byfield. "I'm a really big believer in a high-carbohydrate diet for
athletic performance. I think athletes are really hurting themselves by not getting enough
But when I reported my findings back to my friend Scott, who has played professional
soccer off and on over the past few years and trains regularly, he felt his experience
proved otherwise. Scott followed a modified version of the Atkins diet, eating heavy
amounts of protein but continuing to eat fruits and vegetables as his only source of
carbohydrates-and supplementing with a multi-vitamin.
"I had a heightened amount of energy. I found that during my day- to-day routine, I
never went through the ups and downs of energy that I used to have. I used to get tired,
need to eat, want to take a nap, then need to eat again. Without carbs, I was on a more
steady, higher plateau throughout the day," he said. "With increased energy, I
was able to train a little harder."
So why did Scott seem to benefit from a diet that flies in the face of all scientific
evidence? I don't know. Maybe he was really eating more carbs than he let on (people often
underestimate the carbohydrate they take in in simple sugars, like sugar in their coffee,
etc.) or maybe he has an unusual body chemistry that benefits from a different approach.
The fact that athletes are smashing records right and left, using new training and
nutrition information, such as carbo loading, leaves me thinking that maybe I'll go with
scientific opinion on this one. On the other hand...
Can too Much Protein
We all know that protein is an essential building block in our body's growth, but can an
overdose of protein be bad? According to Dr. Amy Roberts, Coordinator of Sports Science at
the Boulder Center for Sports Medicine and the Sports Science and Asimba Nutrition Editor,
First, it can lead to kidney problems. Our bodies can't metabolize
Nitrogen, one of the components of protein. Because the body disposes of Nitrogen through
the urine, an abundance of protein will not only stress the kidneys but could cause kidney
stones and usually results in dehydration. In fact, individuals eating a high-protein diet
commonly experience a four to five-times increase in urine volume, Roberts says, and this
is doubly harmful when combined with a reduction of carbohydrates in your diet.
Second, it can lead to dehydration. For every gram of glycogen (from
carbohydrates), your body stores three grams of water. Stop eating carbohydrates and you
not only lose the three grams of water with the glycogen, but also lose additional fluids
from excessive urination. The more water you lose, the more you'll need to replace in
order to stay hydrated, according to Roberts.
Roberts prescribes more protein than the USRDA, but still advocates a
carbo-centric diet. An active individual should have about 1.3 grams of protein
per kilo of body weight, each day, she says, and an elite athlete training hard should
increase that amount to about 1.7 g/kg, or roughly 200% USRDA. Research shows that the
human body can't metabolize more than 1.9 g/kg, Roberts adds, and if you're eating more
than that, the protein will be stored as fat.