Last year I did quite a bit of research on diabetes. The first phase insulin response is blunted in pre-diabetics and sucks in diabetics. This first burst seems to play a pretty large role in total post-prandial glucose levels. Not only that, it also seems to be a pretty darn good marker for beta-cell function. If your first phase insulin response sucks, then your beta-cells are likely dying. I came to the conclusion that even though insulin resistance plays an important part, it is not the key. Why is it that many ethnic groups become obese then become diabetic, and others (like Chinese) are thin all the way to diabetes. It may be that most Asians have 30% body-fat but its stored differently, and this is the result of under-nutrition during pregnancy and infancy (1). The lack of amino acids sacrifices subcutaneous fat stores and muscle cells to preserve brain size. Thus while Asian parents are short, the kids born in North America are quite a bit taller. The lack of stores, results in different fat distribution (2). Thus the tall, thin, bald guy with a gut will probably get diabetes.
Anyway, this under-nutrition likely affects the organs as well, specifically the beta-cells which require IGF-1 for stimulation of growth and maintenance. Thus the whole low-protein-low-IGF-1-in-CR-folk-impaired-glucose-tolerance fiasco. The point of all this was to build up to this study:
Diabetes Care. 2013 Feb 12. [Epub ahead of print]
Effects of High-Protein Versus High-Carbohydrate Diets on Markers of β-Cell Function, Oxidative Stress, Lipid Peroxidation, Proinflammatory Cytokines, and Adipokines in Obese, Premenopausal Women Without Diabetes: A randomized controlled trial.
Kitabchi AE, McDaniel KA, Wan JY, Tylavsky FA, Jacovino CA, Sands CW, Nyenwe EA, Stentz FB.
Source
Department of Medicine, University of Tennessee Health Science Center, Memphis, Tennessee.
Abstract
OBJECTIVETo study the effects of high-protein versus high-carbohydrate diets on various metabolic end points (glucoregulation, oxidative stress [dichlorofluorescein], lipid peroxidation [malondialdehyde], proinflammatory cytokines [tumor necrosis factor-α and interleukin-6], adipokines, and resting energy expenditure [REE]) with high protein-low carbohydrate (HP) and high carbohydrate-low protein (HC) diets at baseline and after 6 months of dietary intervention.RESEARCH DESIGN AND METHODSWe recruited obese, premenopausal women ages 20-50 years with no diabetes or prediabetes who were randomized to HC (55% carbohydrates, 30% fat, and 15% protein) or HP (40% carbohydrates, 30% fat, and 30% protein) diets for 6 months. The diets were provided in prepackaged food, which provided 500 kcal restrictions per day. The above metabolic end points were measured with HP and HC diet at baseline and after 6 months of dietary intervention.RESULTSAfter 6 months of the HP versus HC diet (12 in each group), the following changes were significantly different by Wilcoxon rank sum test for the following parameters: dichlorofluorescein (-0.8 vs. -0.3 µmol/L, P < 0.0001), malondialdehyde (-0.4 vs. -0.2 μmol/L, P = 0.0004), C-reactive protein (-2.1 vs. -0.8 mg/L, P = 0.0003), E-selectin (-8.6 vs. -3.7 ng/mL, P = 0.0007), adiponectin (1,284 vs. 504 ng/mL, P = 0.0011), tumor necrosis factor-α (-1.8 vs. -0.9 pg/mL, P < 0.0001), IL-6 (-1.3 vs. -0.4 pg/mL, P < 0.0001), free fatty acid (-0.12 vs. 0.16 mmol/L, P = 0.0002), REE (259 vs. 26 kcal, P < 0.0001), insulin sensitivity (4 vs. 0.9, P < 0.0001), and β-cell function (7.4 vs. 2.1, P < 0.0001).CONCLUSIONSTo our knowledge, this is the first report on the significant advantages of a 6-month hypocaloric HP diet versus hypocaloric HC diet on markers of β-cell function, oxidative stress, lipid peroxidation, proinflammatory cytokines, and adipokines in normal, obese females without diabetes. PMID: 23404297 [PubMed - as supplied by publisher] IGF-1 does seem to play a role in the longevity effects of CR (there are also many other mechanisms). So where does the balance sit? Many on hypocaloric diets choose to lower protein below RDA levels for the sake of IGF-1, but then what about the glucose tolerance? What is known though is that optimal HbA1c levels are actually quite wide, and most likely IGF-1 plays a more important role? But for those of you who know pre-diabetics, get them some protein!
References
1. Science. 1980 Feb 22;207(4433):902-4.Sparing of the brain in neonatal undernutrition: amino acid transport and incorporation into brain and muscle.Freedman LS, Samuels S, Fish I, Schwartz SA, Lange B, Katz M, Morgano L.
2. Body size, body composition, and fat distribution: A comparison of young New Zealand men of European, Pacific Island, and Asian Indian ethnicities
