Fish Oils
Fish Oils Can Make You Thin - by Dr. Mauro Di Pasquale
Dietary fat is often implicated as the primary root cause of the
prevalence of obesity in developed countries. However, research
continues to mount that support all fat is not evil. In fact, some
dietary fat is good. Obesity is of increasing concern in health
issues in the world, surpassed only by cancer and heart disease.
Dietary fat is often implicated as the primary root cause of the
prevalence of obesity in developed countries. However, research
continues to mount that support all fat is not evil. While high
intakes of saturated fat and cholesterol are highly correlated with
obesity, insulin resistance and heart disease, other fats are gaining
respect as actually attenuating these factors. The most favorable
fat in recent research is fish oil.
The benefits of a diet comprised mostly of polyunsaturated fats
are well documented. The essential fatty acids omega-3, 6, and 9
must be obtained from food sources. These fatty acids are the precursors
for several classes of hormones and comprise most of our cell membranes.
Studies are now suggesting that the omega-3 fatty acids are our
friends in a number of ways. Since our modern diet typically is
high in omega-6 fatty acids and low in omega-3 acids, it may prudent
to increase our consumption of foods that contain a higher amount
of omega-3 fatty acids. The richest source of omega-3 fatty acids
is fish oil from cold water fish.
Omega-3 fatty acids improve insulin action and glucose metabolism
in fat and muscle cells. The fatty acids in the phospholipid layer
of cell membranes determine the physiochemical properties of the
membranes. This in turn influences the cellular functions, especially
hormone responsiveness. Increasing the membrane content of polyunsaturated
fatty acids increases membrane fluidity and the binding of many
hormones to their respective receptors, thereby increasing their
action.
They also decrease plasma triglyceride levels. This is hypothesized
and supported by studies to play a role in increasing insulin action.
It involves fuel switching due to increased utilization of glucose.
It is also thought that fish oil supplementation reduces insulin
secretion.
Another important aspect is that a diet derived mostly of it fatty
acids from fish oils (high 0-3:0-6/9) was shown to reduce white
adipose tissue mass, or body-fat, significantly. This has been demonstrated
repeatedly in rat models, and also in humans. While omega-3's also
increased thermogenesis in brown adipose tissue in rats, that probably
has less significance for humans. However, they have detected much
lower levels of enzyme activity for fatty acid synthesis in fish
oil fed rats (and in vitro human fat cells) than in those fed diets
with omega-6, omega-9 and saturated fats. Rats fed diets with omega-3
lost more fat mass (and had much lower triglyceride levels) than
those fed a low-fat, high carb diet that was matched for calories.
They have shown in both rats and humans that the composition of
adipose fatty acids basically resembles the fatty acid composition
of the diet. However, those eating diets high in fish oil EPA and
DHA (omega-3's) were not stored in the adipose tissue in similar
proportion to the concentrations in the diet. Therefore, these fatty
acids may be preferentially oxidized and not stored. Thus, such
rapid fatty acid oxidation might prevent a significant portion of
lipid accumulation.
The other positive benefit is the consumption of a diet high in
0-3 induced an increase in UCP2 in white adipose tissue. Increased
UCP2 uncoupling is associated with reductions in body weight and
white adipose tissue.
Interestingly, a reduction of leptin levels, the fat-stat hormone,
was reported with high omega-3 consumption. However, as most of
the researchers stated in these studies, this may be an artifact
simply due to the reduction in fat mass (leptin is secreted by fat
cells). However, in the studies that reported this, they also demonstrated
a sustained decrease in appetite and no change in energy expenditure
concomitant with decreased leptin levels, which indicates that decreased
leptin levels may not be a concern unless they become acutely low,
such as in a lean person. In that case, rotation or a blend of fatty
acid sources would be necessary. But considering that our diet typically
contains a high ratio of o-6:o-3, that may still be a moot point.
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