Sunday, February 27, 2005

Foods Suspected To Be Functional Foods For Weight Management

A summary of the published review: Dietary fats, teas, dairy, and nuts: potential functional foods for weight control? American Journal of Clinical Nutrition, Vol. 81 No. 1, 7 - 15 January 2005.



Food is our greatest asset and some cultures have used it medicinally for centuries. Today, in our western culture, it's called function foods. Foods have been researched for osteoporosis and cardiovascular disease, so why not obesity ? This newsletter discusses a review of research published in January 2005 looking into four distinct food groups that could help in the prevention of obesity. Later on, we also put together some novel ways of using these ingredients in your recipes.

The functional foods reviewed by Marie-Pierre St-Onge, were dietary fats (specifically medium chain triacylglycerols and diacylglycerols), tea, milk and nuts.

In their review of the literature regarding these four food types, they found that specifically dietary fats may have the most to offer in the fight against obesity, but may only offer benefits in preventing weight gain rather than inducing weight loss.

DIETARY FATS

Medium chain triacylglycerols (MCT) have been studies extensively as they travel directly to the liver instead of through adipose tissue. See the diagram here. This has made the MCT's a hot target for research into weight loss diet and thermogenesis. MCT's can be found when extracted from oils such as coconut oil and the researchers observed that products made with coconut oil were comparable in appearance and taste to those made with conventional cooking oils.

Researchers at the School of Dietetics and Human Nutrition at McGill University recently conducted a 4 week crossover feeding experiment to compare MCT and long chain triacylglycerols (LCT) on energy expenditure and body composition in both men and women. The researchers found that energy expenditure indeed increased when the MCT were consumed more than with those who consumed the LCT's - however thermogenesis was increased slightly. They also found a small trend in lower energy intake after MCT were consumed at breakfast, that is participants tended to eat less after consuming MCT dietary fats.

Research has had some concerns with MCT's though as they have reportedly increased total cholesterol, LDL's, triacylglycerols and glucose concentrations when 70 g of MCT oil was consumed over 21 days. The authors suggest that by combining plant sterols with MCT's total and LDL cholesterol concentrations are lower than those observed after long chain triacylglycerols consumption. So MCT is not without its downside but its undesirable cardiovascular side effects may be able to be counteracted in this way.

Diacylglycerols have also been researched and in some studies found to be even more effective than triacylglycerolds in assisting weight loss. A weight loss study conducted with both obese men and women found that body weight loss was greater in subjects who consumed foods containing diacylglycerols as opposed to those who consumed triacylglycerols, although the percentage change in the intra-abdominal adipose tissue did not differ. The researchers attribute this to diacyclglyercerol's ability to increase energy expenditure, fat oxidation and reduce appetite, but concede that the overall effect is very small and will only be effective when used as a part of a rigorous weight loss plan.

TEA

Tea is the popular beverage that virtually everyone has consumed at some point in their lives. The research has looked into three types of tea, black tea, green tea and oolong tea. While you'll find that many weight loss supplements contain green tea, the research reviewed here found that studies looking into green tea have significant design flaws. Dulbo et. al. found that green tea extract "significantly increased the rate of intrascapular brown adipose tissue oxygen uptake ..... and the authors concluded that green tea extract was a more effective potentiator of sympathetically mediated thermogenesis than caffeine alone." However, this study did not include a control group (a group which receives no treatment so that the treatment group can be compared to it, to see the effect) or a report of the statistical procedures, which nullifies its results somewhat.

Oolong tea however exhibited more promising results. Eleven healthy normal-weight women were tested after drinking water and again after drinking oolong and green tea in random order. The resting energy expenditure "remained low after water and green tea consumption, but increased significantly after oolong tea consumption." These results were more promising, however the study was only conducted over a 2 hour period, which does not give a clear picture of the effects the teas would have over a day.

In conclusion no clear yes, or no observations can scientifically be made about using tea to induce weight loss due to the lack of scientifically controlled and long term research existing at this time.

MILK

There has been widening interest in milk and specifically calcium in fighting obesity, to date no long term studies exist that can prove that milk or calcium have any effect on weight loss per se. While Heaney (1) found that the effects of calcium consumption is somehow linked to body weight regulation, the mechanism by which it works is still unclear and other dietary factors may be playing a role. The author notes that adults who don't eat fast food may drink more milk, while those who do eat fast food, drink less milk. There have been differing results obtained from different studies looking at the effects of dairy and calcium, some finding that there were no effects, while some found beneficial effects for weight loss. (Marie-Pierre St-Onge page 10)

In a study using 41 subjects (32 completed the study) researchers looked at the effects of 400 - 500 mg calcium supplement and a placebo pill(low-dairy group), 400 - 500 mg calcium supplement and 800 mg calcium carbonate (high calcium group) and 400 - 500 mg calcium supplement, a placebo pill, and three servings of dairy products (high dairy group). All subjects initially consumed 1 serving of dairy products. At the end of the study, subjects in the low-dairy, high calcium and high dairy groups lost 6.4%, 8.6% and 10.9% of body weight, while losing 8.1%, 11.5% and 14.1% respectively of fat mass. This data shows that calcium especially from dairy products can enhance weight loss efforts. It was noted that only data from subjects who completed the study (78% of participants) was recorded, so it's not known what effect the other 22% of participants would have had on the results.

While there is some evidence to suggest that milk and calcium may be considered functional foods for weight loss, more research needs to be done to make any conclusions about the functionality of milk and calcium for weight loss.

NUTS

Therefore have been some promising and differing results from research conducted with Almonds, Walnuts, Pistachio, peanut and pecan nuts.

Some studies reviewed here suggested that nuts such as almonds may be able to prevent absorption of energy into the body (2) thereby causing weight loss, while another study found that 100 g almonds consumed per day over 4 weeks produced a slight weight gain.

Most of the studies conducted with the different types of nuts found that there was no weight gain after consuming the nuts, even though the total energy intake had increased. A study conducted with peanuts found that participants resting energy expenditure increased by 11 % after 19 weeks which shows a small increase in overall energy expenditure. The author concludes that while there is some evidence to suggest that nuts may have benefits for weight loss, more research needs to be done and at present only speculation about nuts and weight loss can be made.

Conclusion:

Some foods examined here do have the potential to become weight loss functional foods, but particularly for dairy, nuts and tea, more research realistically needs to be conducted before such claims can be made.

As for dietary fats, there is more research supporting replacing dietary fats with medium chain triaclyglycerols and diaclyglycerols, however it is still unclear what long term effects that they will have and may only be beneficial when used in weight maintenance - not in a weight loss situation and would only be effective when energy restriction and increased physical activity are included in the weight loss plan.

References:

Marie-Pierre St-Onge Dietary fats, teas, dairy, and nuts: potential functional foods for weight control? American Journal of Clinical Nutrition, Vol. 81 No. 1, 7 - 15 January 2005.

(1) Heaney RP Normalizing calcium intake: projected population effects for body weight Journal of Nutrition 2003;133:268S-70S.

(2) Jenkins DJ, Kendall CW, Marchie A, et al. Dose response of almonds on coronary heart disease risk factors: blood lipids, oxidized low-density lipoproteins, lipoprotein(a), homocysteine and pulmonary nitric oxide: a randomized, controlled, crossover trial. Circulation 2002;106:1327-32.

Given that no conclusive conclusions can be made about any of the foods discussed within this paper, but that dietary fats such as those contained within coconut oil may be beneficial in maintaining weight. I thought I'd share some ideas about how to include coconut oil in your diet.

Salad Dressings:

1/4 cup coconut oil
1 tbsp malt vinegar
1 clove of crushed garlic or teaspoon minced garlic
sea salt to taste.

Put all ingredients together and stir until all ingredients mix well.

Cooking Oil:

Mix 1:2 of coconut oil to canola oil and use as you would cooking oil. When you're cooking your favourite steak or shallow frying chicken - coat the pan with this oil.

Wishing you much health and wellness

Jenny Mathers.
Savvy Fat Burning Foods