The Zone Diet

-- The 'Zone Diet' -- Will 'people' ever figure out that diet is not complicated - or do they just need complicated excuses for why they can't lose weight (fat). If weight/fat loss is your goal there is just one important fact: eat more CALORIES than you need you gain - less and you lose, simple.  

>*This hypothalmuspituitary axis is fundamental to the release of hormones like GH, IGF-1,testosterone, cortisol, insulin and glucagon. (129,152).

Are these studies really relevant? Where does it show that the Zone works any better than any other calorically restricted diet? We are certainly not debating what part of the brain controls the release of anabolic and catabolic hormones.

>*Food causes a hormonal, biochemical and metabolic response. (32)

Again, is this study relevant to the Zone? Everyone is in agreement that food causes the changes. Now does the Zone do it any better than any other diet? Where is that part explained?

>*Glucagon response to response and inhibition (19, 203)

I think every one is very well of the glucagon response to low insulin production. Much less the glucagon response to limited carbohydrate intakes. Low insulin and higher glucagon have been demonstrated many times in responses to exercise. No real news here.

>*Fatty acid oxidation increases due to lower liver glycogen from reduced consumption of carbohydrates (66, 137, 138)

I think this has also been shown to be true in prolonged fasting ( Bjorkman & Eriksson, 1983). Gluconeogenesis is also greatly accelerated but total glucose release has been shown to be reduced by as much as 14% to 70% (Phinney et al., 1983). So we eat more fat and use more fat, but as carbohydrate intakes dwindle, so does muscle glycogen synthesis. This could be a problem for those that use lost of muscle glycogen. Even with Phinney's extreme diet, it seems clear that fat oxidation cannot be increased sufficiently to fully replace muscle glycogen as a source of energy for intense exercise.

>*You don't need the large amounts of insulin from high carb diets to store protein and glucose. Too much insulin will activate fat storage and make muscles more resistant to insulin. This is why many people exercise to death but still can't get rid of the bulge. (8, 77, 164).

No, I agree with this. Even small amounts of insulin will do the job. However, plasma FFA mobilization is remarkably sensitive to even small increases in plasma insulin (Jensen et al., 1989), diets that are lower in carbohydrate or that contain carbohydrates that cause less insulin secretion, probably still elicit enough of an insulin response to reduce plasma FFA mobilization. Now too much fat has also been shown to keep insulin from doing its job (Barnard, 1990).Insulin is needed to turn off appetite for fats and carbohydrates (Leibowitz, 1995). High fat has also been shown to increase the hormone leptin which has also been suspected to in crease appetite.

>*Your body can store and average of 1600 to 2000 calories from carbohydrates. The higher the blood levels of glucose, the less fat can be released for metabolism. (5, 36, 48, 116)

Yes, while the body can only store these amounts, the brain requires another 25% and activity may use the rest. It is a well known fact that blood glucose interferes with FFA metabolism, however, plasma FFA mobilization is remarkably sensitive to even small increases in plasma insulin (Jensen et al., 1989), diets that are lower in carbohydrate or that contain carbohydrates that cause less insulin secretion, probably still elicit enough of an insulin response to reduce plasma FFA mobilization.

>Benefits of Zone or Iso-caloric eating *Glucagon freely mobilized to aid body fat release. (135,136,191)

No big news here, but cortisol production is also increases. I think that you will find that insulin spikes (lower glucagon) also produce more testosterone (Pasquali, 1995)

>*Increased protein sparing effect and nitrogen retention (65, 135, 136)

Check out these studies...Lemmon and Mullin (1980) show protein utilization during exercise is stimulated with carb (or calorie) restriction. Motil et al. (1981) found that protein utilization is increased in resting humans by a high protein diet. All were low carb/high fat diets. Both showed not only nitrogen excretion was greater, but they also showed that leucine oxidation was much greater. Knapik et al. (1991) showed that leucine was utilized at a greater rate, thus reducing greatly the amounts of leucine needed for muscle protein synthesis. Inadequate carb intake during intense could increase protein oxidation, thus adversely affecting adaptations to training (Coggan, 1992).

>*Lowers LDL and plasma triglycerides and increases HDL (85, 115,142,196)

OK...once again who is saying that monounstaurates are not healthier. There is lots of evidence that suggest that. There is also lots of evidence that suggest that omega-3 fish oils are healthy. However, 8 oz. of salt water fish per week could easily provide the necessary omega-3 oils we need. Certainly we would benefit from using monounsaturates instead of so much of the saturates. Still this doesn't prove that the Zone is any better than any other diet.

>*Production of "good" eicosanoids stimulate GH and testosterone from >controlled insulin and essential fatty acid consumption. (39, 53, 163, 168, >170, 186)

Ooops, you didn't include that last reference (186). OK, so it is excepted that fats are needed in the diet to produce testosterone. No news here. I would recommend anyone who is interested in building muscle or strength to consume more fat. The other reference only tells us that when the insulin production drops, glucagon production increases as does GH release. No news here either! Exercise can easily accomplish this.

>Failures of the low-fat/ high carbohydrate diet: >*Sporadic insulin promotes fat storage (insulin is anti-lipolytic) >(7,48,148,164)

True, only when there are sufficient calories. Big deal!

>*Low glucagon because carbs are needed to offset the yo-yo effect of blood sugar (32,54,148)

This may be true for those that eat large amounts of sugar.

>*Limits fat oxidation and increases fat storage (8, 40, 59, 87)

No, fats are not oxidized as quickly, but they don't need to be because they are not in great supply. Fat oxidation is increased in fasting and low carb/high fat diets only because the are in greater supply. Horton et al. (1995) found that carbohydrate overfeeding produced progressive increases in carbohydrate oxidation and total energy expenditure resulting in 75-85% of excess energy being stored. Alternatively, fat overfeeding had minimal effects on fat oxidation and total energy expenditure, leading to storage of 90-95% of excess energy. Excess dietary fat leads to greater fat accumulation than does excess dietary carbohydrate, and the difference was greatest early in the overfeeding period. Remember that fats do not appreciably raise the thermogenesis. So when there are an abundance of calories a much larger percentage of the 9 cal/g are stored as fat.

>*Reliance on glycogen for energy decreases nitrogen retention by increasing gluconeogenesis during exercise. (102, 197, 198)

In a higher carb diet, the available supply of muscle glycogen IS greater. In a low carb diet, gluconeogenesis is also greatly accelerated but total glucose release has been shown to be reduced by as much as 14% to 70% (Phinney et al., 1983). Low carb intakes also reduce the available supply of glycogen for use. Once again, Lemmon and Mullin (1980) show protein utilization during exercise is stimulated with carb (or calorie) restriction. Motil et al. (1981) found that protein utilization is increased in resting humans by a high protein/low carb diet. Both showed not only nitrogen excretion was greater, but they also showed that leucine oxidation was much greater. Knapik et al. (1991) showed that leucine was utilized at a greater rate, thus reducing greatly the amounts of leucine needed for muscle protein synthesis. Inadequate carb intake during intense could increase protein oxidation, thus adversely affecting adaptations to training (Coggan and Mendenhall, 1992).

>*Inhibits fat burning enzymes, activates fat storing enzymes and is considered fat sparing. (87, 119, 141)

I think that Phinney et al. (1983) demonstrated that even small amounts of dietary carbohydrate might negatively influence fat metabolism. Is it not more important to do long duration, low intensity exercise to low insulin, raise glucagon, use carbs, and release and oxidize FFA. The Zone fails to emphasize this.

While you have demonstrate the ability to scan lots of meaningless references in to your hard drive. You have still failed to produce any relevant studies that show how the Zone is any better in reducing weight than any other more conventional approaches. Any possible benefits of the Zone could more easily be gained through exercise. What you and the Zone seem to under emphasize of even thumb you nose at is the importance of lifestyle changes like exercise. No doubt this lack of exercise is the real key to many of the health and weight problems many modern Americans experience. I still agree that by eating a variety or foods, lowering fat intakes (especially saturates), lowering the consumption of sugars and salt, increasing the consumption of fiber, decreasing the amount of daily calories, and increasing the amount of exercise, one can live a long, happy, healthy life. You certainly don't need to buy a book, PR Bars, call a 1-800 number or subscribe to a Zone mailing list to do this.

The following is a quote from Dr. A.R.Coggan: "If homo sapiens were too dependent on having the ideal "balanced" diet, we wouldn't have come to dominate this planet the way we do!"

References:

Barnard RJ, et al. (1990). Plasma glucose and insulin responses to traditional Pima Indian meals. Am. J. Clin. Nutr. 51:416-20.

Bjorkman, O. and L.S. Eriksson (1983). Splanchnic glucose metabolism during leg exercise in 60-h fasted human subjects. Am. J. Physiol. 245 (Endocrinol. Metab. 8):E443-E448.

Coggan, A.R. and M.A. Mendenhall. Effects of diet on substrate metabolsim during exercise. IN: Perspectives in Exercise Scince and Sports Medicine: Volume 5 Energy Metabolism in Exercise and Sport. D.R. Lamb and C.J. Gisolfi (eds). Brown and Bench, Dubuque, IA. 1992. pp. 435-458. Horton, T.J., et al. (1995). Fat and carbohydrate overfeeding in humans: different effects on energy storage. Am. J. Clin. Nutr. 62:19-29.

Jensen, M.D., M. Caruso, V. Heiling, and J.M Miles (1989). Insulin regulation of lypolysis in nondiabetic and IDDM subjects. Diabetes 38:1595-1601.

Knapik, J. C., et al. (1991). Leucine metabolism during fasting and exercise. J. Appl. Physiol. 70:43-47.

Leibowitz. S.F. (1995). Insulin Plays Role in Controlling Fat Craving.Rockefeller University News. Saturday, Aug. 13.

Lemmon, P.W.R. and J.P. Mullin (1980). Effect of initial muscle glycogen levels on protein catabolism during exercise. J. Appl. Physiol. 48:624-629.

Motil, K.J. et al. (1981). Whole body Isoleucine and lysine metabolism: response to dietary protein intake in young men. Amer. J. Physiol. 240:E717-E721.

Pasquali, R. et al. (1995). Insulin regulates testosterone and sex hormone-binding globulin concentrations in adult normal weight and obese men. J. Clin. Endocrinol. Metab. 80:654-658.

Phenney, S.D., et al. (1983). The human metabolistic response to ketosis withoout caloric restriction: preservation of submaximal exercise capability with reduced carbohydrate oxidation. Metabolsim. 32:769-776.