Re: Avoid The Zone (40/30/30)

[Guest guest]

J Clin Endocrinol Metab. 2004 Sep;89(9):4197-205. Diet, insulin resistance, and obesity: zoning in on data for Atkins dieters living in South Beach.Lara-Castro C, Garvey WT. Department of Nutrition Sciences, Webb 232, University of Alabama at Birmingham, 1675 University Boulevard, Birmingham, Alabama 35294-3360, USA. Insulin resistance is a central pathogenic factor for the metabolic syndrome and is associated with both generalized obesity and the accumulation of fat in the omental and intramyocellular compartments. In the context of the current obesity epidemic, it is imperative to consider diets in terms of their ability to both promote weight loss and ameliorate insulin resistance. Weight loss under any dietary formulation depends on hypocaloric intake, and only moderate weight loss (5-10%) is sufficient to augment insulin sensitivity. However, increments in insulin sensitivity may be more directly related to loss of

intramyocellular or omental fat rather than loss of total body weight per se. The widespread acceptance of popular low-carbohydrate high-fat diets (e.g. Atkins Diet, Zone Diet, South Beach diet) further underscores the need to evaluate dietary interventions regarding their safety and metabolic effects. These high-fat diets have been shown to be safe in the short term; however, their long-term safety has not been established. With respect to insulin sensitivity, diets enriched in saturated fats can induce insulin resistance, whereas fat substitution with monounsaturated fats can enhance insulin sensitivity. On the other hand, high-fiber, high-carbohydrate diets comprised of foods with low caloric density can similarly be used for effective weight reduction and to ameliorate insulin resistance. Although some data suggest that low-glycemic index diets are most advantageous in this regard, these effects may have more to do with increments in dietary

fiber than differences in available carbohydrates. Popular low-carbohydrate, high-fat diets are being fervently embraced as an alternative to challenging modifications in lifestyle and intentional calorie reduction. Current data do not support such unbridled enthusiasm for these diets, particularly in relationship to high-fiber, high-carbohydrate diets emphasizing intake of fresh vegetables and fruits. Long-term studies to determine the efficacy and safety of both popular and experimental diets are warranted. PMID: 15356006 J Am Coll Nutr. 2003 Feb;22(1):9-17. Links The Zone Diet phenomenon: a closer look at the science behind the claims.Cheuvront SN.U.S. Army Research Institute of Environmental Medicine, Natick, Maine 01760, USA. samuel.cheuvront@... The purported health benefits of

low-carbohydrate diets have been advocated intermittently over the last century and have enjoyed increasing popularity over the last decade. Although most revolve around the emphatic theme that carbohydrates are to blame for many chronic diseases, their specific ideologies are more variable and in some cases quite sophisticated. The Zone Diet phenomenon represents a new generation of modern low carbohydrate food fad with sales placing it among the most popular diet books in recent history. The Zone is a 40% carbohydrate, 30% protein and 30% fat eating plan that advocates only sparing use of grains and starches. The precise 0.75 protein to carbohydrate ratio required with each meal is promoted to reduce the insulin to glucagon ratio, which purportedly affects eicosanoid metabolism and ultimately produces a cascade of biological events leading to a reduction in chronic disease risk, enhanced immunity, maximal physical and mental performance, increased longevity and permanent

weight loss. There is presently little scientific support for the connections made between diet, endocrinology and eicosanoid metabolism. In fact, a review of the literature suggests that there are scientific contradictions in the Zone Diet hypothesis that cast unquestionable doubt on its potential efficacy. The purpose of this review is to evaluate the scientific merit of the Zone Diet and its health claims in an effort to help delineate what is and what is not sound nutrition science. Key teaching points: • There is no evidence that a 0.75 protein to carbohydrate ratio (40/30/30), whether eaten as a small test meal or in the form of a complete mixed diet, reduces the insulin response when compared to traditional dietary guideline meal/food intakes and may even potentially produce a larger area under the insulin curve. • Although carbohydrate, protein, insulin and glucagon can

impact delta destaurase enzyme activity, those activities reported by the Zone clearly and selectively ignore the known effects of macronutrients and hormones that contradict the Zone theory. • The scientific literature is in opposition to the purported benefits of adopting a Zone Diet for improved health. Sports Med. 1999 Apr;27(4):213-28. Links The zone diet and athletic performance.Cheuvront SN.Department of Nutrition, Food, and Exercise Sciences, Florida State University, Tallahassee, USA. The Zone diet is the latest eating regimen marketed to improve athletic performance by opposing traditional high carbohydrate sports diets. The 40/30/30 diet is centred primarily on protein intake (1.8 to 2.2 g/kg fat free mass; i.e. total bodyweight-fat weight) and promises a change in the body's insulin to glucagon ratio through its

macronutrient alterations. Changes in the existing hormonal milieu are said to result in the production of more vasoactive eicosanoids, thus allowing greater oxygen delivery to exercising muscle. This favourable condition, known as the Zone, is anecdotally reported to benefit even the most elite endurance athletes. Applying the Zone's suggested protein needs and macronutrient distributions in practice, it is clear that it is a low carbohydrate diet by both relative and absolute standards, as well as calorie deficient by any standard. Reliable and abundant peer reviewed literature is in opposition to the suggestion that such a diet can support competitive athletic endeavours, much less improve them. The notion that a 40/30/30 diet can alter the pancreatic hormone response in favour of glucagon is also unfounded. The Zone is a mixed diet and not likely to affect pancreatic hormone release in the same way individual nutrients can. Although the postprandial insulin response is

reduced when comparing a 40% with a 60% carbohydrate diet, it is still a sufficient stimulus to offset the lipolytic effects of glucagon. Many of the promised benefits of the Zone are based on selective information regarding hormonal influences on eicosanoid biology. Contradictory information is conveniently left out. The principle of vasodilating muscle arterioles by altering eicosanoid production is notably correct in theory. However, what little human evidence is available does not support any significant contribution of eicosanoids to active muscle vasodilation. In fact, the key eicosanoid reportedly produced in the Zone and responsible for improved muscle oxygenation is not found in skeletal muscle. Based on the best available scientific evidence, the Zone diet should be considered more ergolytic than ergogenic to performance. PMID: 10367332

[Guest guest]

Barry

Sears claims about athletic performance and the Zone have always been

bunk.

Your body

has multiple systems for producing energy -- it can metabolize fat,

protein and carbohydrates. The carbohydrate system is the one

capable of the highest throughput -- to go above 50-65% of your aerobic

max, you need to burn carbohydrates... This can be from a

meal you just ate or it can be stored glycogen.

I can walk

all day on a ketogenic diet, but I can't run.

When I was

doing a " zone " diet I found I had to add extra carbs to top off

my glycogen. It's often claimed that your muscles will really soak

up carbohydrates after a workout, so I'd eat a few rice

cakes, something really high glycemic.

On a

regimen of

2x a week: ~1 hour of aerobic workout

3x a week: ~ 1/2 of aerobics, 45 min of weight training

and a

zoneish diet I had the lowest weight I've ever had, also the lowest

blood pressure. That said, when I went to a more free-feeding

diet and 2x a week weight training, I had a pretty rapid increase

in how much I can lift, but I also gained fat and had my BP go back

up.

At 09:36 AM 7/20/2006, you wrote:

Sports Med. 1999

Apr;27(4):213-28. Links

The zone diet and athletic performance.

Cheuvront SN.

Department of Nutrition, Food, and Exercise Sciences, Florida State

University, Tallahassee, USA.

The Zone diet is the latest eating regimen marketed to improve athletic

performance by opposing traditional high carbohydrate sports diets. The

40/30/30 diet is centred primarily on protein intake (1.8 to 2.2 g/kg fat

free mass; i.e. total bodyweight-fat weight) and promises a change in the

body's insulin to glucagon ratio through its macronutrient alterations.

Changes in the existing hormonal milieu are said to result in the

production of more vasoactive eicosanoids, thus allowing greater oxygen

delivery to exercising muscle. This favourable condition, known as the

Zone, is anecdotally reported to benefit even the most elite endurance

athletes. Applying the Zone's suggested protein needs and macronutrient

distributions in practice, it is clear that it is a low carbohydrate diet

by both relative and absolute standards, as well as calorie deficient by

any standard. Reliable and abundant peer reviewed literature is in

opposition to the suggestion that such a diet can support competitive

athletic endeavours, much less improve them. The notion that a 40/30/30

diet can alter the pancreatic hormone response in favour of glucagon is

also unfounded. The Zone is a mixed diet and not likely to affect

pancreatic hormone release in the same way individual nutrients can.

Although the postprandial insulin response is reduced when comparing a

40% with a 60% carbohydrate diet, it is still a sufficient stimulus to

offset the lipolytic effects of glucagon. Many of the promised

benefits of the Zone are based on selective information regarding

hormonal influences on eicosanoid biology. Contradictory information is

conveniently left out. The principle of vasodilating muscle

arterioles by altering eicosanoid production is notably correct in

theory. However, what little human evidence is available does not support

any significant contribution of eicosanoids to active muscle

vasodilation. In fact, the key eicosanoid reportedly produced in the Zone

and responsible for improved muscle oxygenation is not found in skeletal

muscle. Based on the best available scientific evidence, the Zone diet

should be considered more ergolytic than ergogenic to performance.

PMID: 10367332

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