Maintaining an ideal body weight is important for good health,
and the right diet can facilitate this goal. Unfortunately, promises
of fast, easy weight loss draw many people to fad diets. High-protein,
carbohydrate-restricted diets are no exception. Popular in the 1970s
and again today (as U.S. obesity rates reach an all-time high),
the Atkins Diet and similar programs fail to address critical health
implications of diets that emphasize animal products.
What the Weight-Loss
Studies from Duke University,1 the University
of Pennsylvania,2 and Philadelphia Medical
Center3 suggest that average weight loss
with high-protein diets during the first six months of use is approximately
20 pounds—not demonstrably greater than results from other
weight-loss regimens. Additionally, a review of 107 research studies
on carbohydrate-restricted diets found that the amount of carbohydrate
consumed had no effect on the degree of weight loss.
High-protein diets are designed to induce ketosis, a condition that
occurs in uncontrolled diabetes mellitus and starvation. When there
are not enough carbohydrates in the diet to provide glucose to the
cells that rely on it as an energy source, ketone bodies are formed
from fatty acids. An increase in circulating ketones can disturb
the body’s acid-base balance, causing metabolic acidosism,
which can lead to hypophosphatemia, resorption of calcium from bone,
osteoporosis, and kidney stones.6
Regular meat consumption increases colon cancer risk by about 300
percent, according to research from Harvard University. High-protein
diets emphasize animal products and therefore are typically low
in dietary fiber, which facilitates the movement of wastes, including
carcinogens, out of the digestive tract, and promotes a biochemical
environment within the colon that appears to be protective against
Typical high-protein diets are extremely high in dietary cholesterol
and saturated fat. The effect of such diets on serum cholesterol
concentrations is a matter of ongoing research. However, evidence
indicates that meals high in saturated fat impair arterial compliance.
A recent study showed that the consumption of a high-fat meal (ham-and-cheese
sandwich, whole milk, and ice cream) reduced systemic arterial compliance
by 25 percent at three hours and 27 percent at six hours.9
High-protein diets are associated with reduced kidney function,
which, over time, can lead to permanent loss of kidney function.
These diets are associated with a significant decline in kidney
function, according to research from Harvard University monitoring
1,624 women participating in the Nurses’ Health Study. While
kidney damage was found only in those who already had reduced kidney
function, this condition is far from rare and currently affects
as many as one in four U.S. adults. Plant protein, on the other
hand, had no harmful effect.10
Very high protein intake is known to encourage urinary calcium losses
and has been shown to increase risk of bone fractures in research
With diabetes, kidney and heart problems are particularly common.
The use of diets that further tax the kidneys and may reduce arterial
compliance is not recommended.
The American Heart Association states, “High-protein diets
are not recommended because they restrict healthful foods that provide
essential nutrients and do not provide the variety of foods needed
to adequately meet nutritional needs. Individuals who follow these
diets are therefore at risk for compromised vitamin and mineral
intake, as well as potential cardiac, renal, bone, and liver abnormalities
A Healthier Way to
Of the many ways to lose weight, one stands out as by far the most
healthful. When meals are built from a generous array of vegetables,
fruits, whole grains, and beans—that is, healthy vegetarian
choices—weight loss is remarkably easy. And along with it
come major improvements in cholesterol, blood pressure, blood sugar,
and many other aspects of health. The answer is simple: Cut out
the foods that are high in fat and devoid of fiber, and increase
the foods that are low in fat, rich in fiber, and most nutritious.
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3. Samaha FF, et al. A low-carbohydrate as compared with a low-fat
diet in severe obesity. N Engl J Med 2003;348:2074-81.
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RH; Nutrition Committee of the Council on Nutrition, Physical Activity,
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Food, Nutrition, and the Prevention of Cancer: a global perspective.
World Cancer Research Fund/American Institute for Cancer Research,
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The Impact of Protein Intake on Renal Function Decline in Women
with Normal Renal Function or Mild Renal Insufficiency Ann Int Med
11. Nestel PJ, Shige H, Pomeroy S, Cehun M, Chin-Dusting J. Post-prandial
remnant lipids impair arterial compliance. J Am Coll Cardiol 2001;37:1929–35.
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Am Fam Physician 1999;60:2269–76.
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between dietary animal protein and hip fracture: a hypothesis. Calcif
Tissue Int 1992;50:14–18.
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and bone fractures in women. Am J Epidemiol 1996;143:472–9.
15. Reddy ST, Wang CY, Sakhaee K, Brinkley L, Pak CY. Effect of
low-carbohydrate high-protein diets on acid-base balance, stone-forming
propensity, and calcium metabolism. Am J Kidney Dis 2002;40:265–74.
16. Gin H, Rigalleau V, Aparicio M. Lipids, protein intake, and
diabetic nephropathy. Diabetes Metab 2000 Jul;26 Suppl 4:45–53.
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