cron-web.org

[A1CR]

It appears that the important factor may be the use of CR
for our response
to the amount and glycemic index of our carbohydrates
intakes, the below
review paper.

Anastassios G. Pittas and Susan B. Roberts.
Dietary Composition and Weight Loss: Can We Individualize
Dietary
Prescriptions According to Insulin Sensitivity or Secretion
Status?
Nutrition Reviews, Oct 2006, Vol. 64 Issue 10, p435-448, 14p

Insulin Secretion and Response to Hypocaloric Diets

There has been very limited exploration of the effects
of insulin secretion on weight loss response to
hypocaloric diets in intervention trials (Table 4). Initial
evidence for an important role of insulin secretion in
energy balance and weight loss comes from pharmacologic
studies in which insulin secretion was suppressed
with pharmacologic agents and weight loss response
assessed. In one such study, obese participants were all
given a hypocaloric diet and then randomized to either
placebo or diazoxide, a K^+[ATP] channel agonist that
decreases insulin secretion and is used in the medical
management of insulinomas.60 Compared with the placebo
group, the diazoxide group lost more weight (4.6
vs. 9.5 kg, respectively) while on the hypocaloric diet,
supporting an important role for insulin secretion in
modifying weight loss in response to caloric restriction.

In another pharmacologic study in obese individuals,
insulin secretion was suppressed by octreotide-LAR,
a somatostatin analog used in various endocrine hypersecretory
conditions, without a concomitant lifestyle intervention.
61 For the entire cohort, significant insulin
suppression was achieved with accompanied weight loss
and decreased self-reported carbohydrate craving. In a
post hoc analysis, participants who lost the most weight
exhibited the highest suppression in pancreatic beta-cell
activity and the highest reduction in carbohydrate cravings
and intake. During the baseline oral glucose tolerance
test, this group exhibited a rapid increase and a high
peak in insulin level, followed by a rapid decline, suggesting
that first-phase insulin hypersecretion (first 30
min) may be particularly important. Although insulin-independent
effects of octreotide cannot be ruled out
(such as effects on incretins, gastric motility, etc.), the
results of this pharmacologic study, which was done
without an accompanied caloric restriction prescription,
provide further support for an important role of insulin
hypersecretion in the genesis of obesity.

There are other types of data that are broadly consistent
with the hypothesis that insulin secretion status
influences weight loss. In a study of women given a
hypocaloric diet for weight loss, those with central adiposity
who also had higher insulin secretion and higher
insulin resistance lost more weight compared with a
group of woman with peripheral adiposity who had
lower insulin secretion and lower insulin resistance.55 In
contrast, in a post hoc analysis of a non-randomized,
non-controlled, short-term intervention study in women
given a hypocaloric diet (43% carbohydrate, 15% protein,
and 42% fat), the baseline integrated insulin response
(as measured by the meal tolerance test, MTTINSAUC-
8hr) to two consecutive meal challenges did not
predict weight loss in response to the diet.54 However,
this study was small (N=20) and no adjustments were
made for other important factors such as menopausal
status.

In summary, the contribution of insulin secretion to
future weight and response to hypocaloric diets, including
those that vary in macronutrient composition, is
controversial and its effects are difficult to isolate from
insulin resistance. However, baseline insulin secretion
status may be important with regard to dietary macronutrient
composition, as discussed below.

INSULIN SECRETION AND RESPONSE TO
HYPOCALORIC DIETS OF VARYING
MACRONUTRIENT COMPOSITION

Although the topic of whether insulin secretion affects
the ability of overweight individuals to lose weight
in response to a non-specific hypocaloric diet is a new
and important area for study, the influence of insulin
hypersecretion in modulating weight loss may be particularly
important for specific dietary compositions, in
particular diets that differ in GL. 29,62 This hypothesis is
suggested by animal studies63,64 and results from a recent
human study in our laboratory.35

As described above, weight loss studies with varied
macronutrient composition, including those using the
concept of the dietary GL, have shown conflicting results
for heterogeneous groups of individuals.31,32,34,37,65-67
As a result, currently there is no general consensus about
the relative benefits or disadvantages of these types of
diets for weight loss in the general population. However,
our new findings35 may provide an explanation for the
conflicting results seen in human studies of weight loss
utilizing a variety of macronutrient compositions, since
none of these studies examined the effects of the different
diets stratified by baseline insulin secretion or other
measures of metabolic status.

We recently completed a small, randomized, double-blind,
controlled feeding trial in healthy overweight
adults to examine the weight loss effects of two hypocaloric
diets differing in GL. Participants were randomized
for 24 weeks to a provided diet with either a high GL
(60% carbohydrate, 20% protein, 20% fat, fiber 15
g/1000 kcal, mean estimated daily GI of 86 and GL of
116 g/1000 kcals) or a low GL (40% carbohydrate, 30%
protein, 30% fat, fiber 15 g/1000 kcal, mean estimated
daily GI of 53 and GL of 45 g/1000 kcals) at 30% calorie
restriction compared with baseline individual energy
needs. In a post hoc multivariate prediction analysis, we
examined whether the weight loss effects of the two diets
varied according to baseline insulin secretion and insulin
resistance. Simple indices of insulin secretion, insulin
level 30 minutes after glucose loading (INS30) and homeostasis
model assessment-insulin resistance (HOMAIR)
were examined for their ability to predict change in
weight from baseline to 6 months. A total of 32 (25
women and 7 men) out of 34 enrolled participants completed
the 6-month intervention. At baseline, mean fasting
glucose was 84 mg/dL and insulin was 11.5 mU/L.
Both groups achieved statistically significant (P <
0.001) weight loss compared with their baseline weight.
Adjusted for baseline weight and other baseline variables,
weight loss was equivalent in the two groups both
at 3 and 6 months.

In multivariate prediction models, there was no
diet × HOMA-IR interaction, but there was a diet ×
INS30 interaction (P=0.02). Therefore, we examined
the weight data stratified into two groups separated by
the median INS30 value (Figure 1). Participants with
relatively high baseline INS30 lost more weight if randomized
to the low-GL diet compared with the high-GL
diet (P < 0.05). In participants with relatively low
baseline INS30, those in the high-GL diet group lost more
weight than those in the low-GL diet group, but the
difference was not statistically significant. We concluded
that in healthy overweight individuals examined without
respect to their baseline metabolic profile, calorie-restricted
diets of varying GL result in equivalent weight
loss. However, based on the multivariate analysis, a
calorie-restricted diet low in GL led to more weight loss
in those who had relatively higher stimulated insulin
secretion at baseline.35

Our participants were not particularly insulin resistant,
and therefore the lack of relative insulin resistance
in those with high insulin release may have predisposed
this group of individuals to weight gain. This was suggested
by the data from Sigal et al.,44 and was reversed
by a low-GL diet. ...