Fish-rich Diets May Help Balance Leptin Levels

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Fish-rich Diets May Help Balance Leptin Levels

 

Leptin is small protein that's gotten a lot of press in the past few

years. Because it's able to act like a hormone, and is connected

with fat metabolism, leptin has become a molecule of interest to

many researchers - including drug companies - who see leptin as a

possible tool in weight management. Results in the drug development

area have not been very promising so far. However, during this

period of time, we've learned some interesting facts about leptin,

diet, and health.

 

First, exceeding low or high levels of leptin in our bloodstream

appear to reflect health problems. High levels are associated with

obesity, and also with higher percentages of body fat. High levels

may also signify a change in the body's sensitivity to leptin, where

the body may have lost some of its responsiveness to this protein.

 

Low levels appear to be associated with increased appetite, and

difficulty reaching puberty during development. Most of the research

in the above areas has been conducted on animals.

 

If possible, we would probably want to avoid both of the extremes

described above. In terms of diet, one approach to avoiding these

extremes may involve the level of fish we include in our meal plan.

 

Thanks to a study conducted on two African tribes and published in

the July 2002 issue of Circulation: Journal of the American Heart

Association, we may have gotten one clue about avoiding extremes in

our blood leptin levels.

 

In this study, higher levels of leptin, potentially associated with

problems regulating fat metabolism, were found in low-fish diets.

Fish-rich diets were associated with lower leptin levels and

potentially fewer problems in regulating fat metabolism.

 

Practical Tips

Here are a few quick serving ideas from the World's Healthiest Foods

to help you balance your leptin levels by enjoying fish more often:

 

Combine cod, vegetable broth, healthy sautéed onions and garlic, and

your favorite vegetables and seasonings in a stock pot to make a

delicious fish soup.

Make fish tacos by wrapping halibut, salsa and guacamole in a

tortilla.

Marinate snapper in citrus juice and honey, then bake.

 

The researchers compared leptin levels in two closely related

African tribal populations living in Tanzania. The two groups are

essentially the same tribe, but they're separated geographically.

One group lives close to a lake, while the other lives inland. The

inland-dwelling tribe eats a diet high in fruits and vegetables,

while for the tribe living by the lake, freshwater fish is a main

component of the diet.

 

The researchers studied 279 people on the high fish diet and 329 who

ate the vegetarian diet. They compared average daily calorie intake

and food consumption, BMI (body mass index, a measure of body fat

based on height and weight), body fat content, age and gender. Skin-

fold thickness was also used to assess body fat. Leptin, insulin and

glucose levels were measured after an overnight fast.

 

The average BMI among the people in the study, regardless of diet,

was 20. A BMI value from 18.5 to 24.9 is considered healthy; BMI

from 25.0 to 29.9 is overweight; and a BMI value of 30 or greater is

obese.

 

Average daily calorie intake was similar for both groups-2196 for

the fish-rich diet and 2109 for the vegetarian diet. The fish-rich

diet consisted of 300-600 grams (or approximately 10-20 ounces) of

fish per day, with 40-60g of beans, 20-40g of spinach, 40-60g of

potatoes and 30-50g of rice. The vegetarian diet included negligible

amounts of fish with 70-140g of beans, 60-100g of spinach, 100-200g

of potatoes and 80-120g of rice.

 

Among those on the fish diet, men had average leptin levels of 2.5

nanograms per milliliter (ng/mL), and women had an average of 5.0

ng/mL. In comparison, among the tribe eating primarily vegetables,

men had average leptin levels of 11.2 ng/mL, and women had average

levels of 11.8 ng/mL.

 

Leptin, which is secreted by fat tissue, may act as a satiety

messenger, which in normal-weight people signals " stop eating, " when

they have consumed enough food.

 

As people gain weight, however, the body may stop listening to

leptin's message, so more leptin may be produced to get the message

across, explains senior author Virend K. Somers, M.D., D. Phil.,

professor of medicine in the division of cardiovascular disease and

hypertension at the Mayo Clinic, Rochester, Minn.

 

Among the African populations in this study, however, higher body

fat was not clearly associated with increased leptin

levels. " Regardless of body fat or body mass index (BMI), leptin

levels were substantially lower among the fish-eaters than among

vegetarians, " says Somers.

 

" We speculate that a fish diet may change the relationship between

leptin and body fat and somehow help make the body more sensitive to

the leptin message. "

 

Leptin's effects on health are not limited simply its relation role

in satiety and fat metabolism,

but higher levels also correlate with insulin resistance and other

markers of the metabolic syndrome, popularly dubbed " Syndrome X, " in

which the body's ability to effectively utilize glucose lessens.

Syndrome X is thought to be an initial warning sign of increasing

risk for type 2 diabetes.

 

An earlier study of more than 1,000 men in Scotland published in

Circulation in 2001 found that high leptin levels could be used to

identify men at increased risk for a heart attack. For each standard

deviation increase in leptin levels, the men's relative risk for

heart attack increased by 125%.

 

In this study, leptin levels were found to correlate with levels of

C-reactive protein, a marker of inflammation that is a coronary

heart disease risk factor considered even more significant than

cholesterol levels.

 

The higher the men's leptin levels, the higher their C-reactive

protein.

 

In the African tribe study, lead researcher Somers says the low

leptin levels among the fish-eating women were particularly

noteworthy. Women usually have higher leptin levels than men, but in

this study, women who ate the fish-rich diet had lower leptin levels

than either the women or the men on the vegetarian diet.

 

Somers says this finding fits with earlier studies that showed diets

high in fish were associated with an improved cardiovascular risk

profile, and adds

" These results add to the increasing body of evidence pointing to

the benefits of fish consumption. "

 

Fish consumption is very low in most American's diets, although The

American Heart Association recommends at least two servings of fish

a week.

 

References: Somers V, Winnicki M, Phillips B, Accurso V, Puato M,

Palatini P, Pauletto P. Fish-rich tribal diet linked with low leptin

levels. July 2, 2002 Rapid Access Issue, Circulation. Wallace AM,

McMahon AD, Packard CJ, Kelly A, Shepherd J, Gaw A, Sattar N. Plasma

leptin and the risk of cardiovascular disease in the west of

Scotland coronary prevention study (WOSCOPS). Circulation 2001 Dec

18;104(25):3052-6.