Tuesday, 11 March 2008

My Big Fat Diet

Did you watch 'My Big Fat Diet' on CBC tonight?

We know that obesity and Type 2 diabetes is prevalent among the aboriginal population. According to some sources, its 5 times the national average. Their genetic predisposition combined with their change of diet (introduction of the Wesern diet into their communities) and lifestyle (now more sedentary) is undoubtedly the culprit.

Dr. Jay Wortman, a m├ętis doctor and a Type 2 diabetic himself, noticed that when he cut out carbohydrates (starches and sugars) from his own diet, his blood sugar and blood pressure normalized.
He decided to design a study where he'd get 100 members of the Namgis First Nation from Alert Bay, BC to cut out all carbohydrates from their diet- all starches as well as fruit and milk- for one year. The study was funded by UBC and Health Canada and is still being evaluated.

The study diet is supposed to be based on a traditional native diet but also includes modern market foods.

Any meat was permitted as part of the diet- beef, pork, chicken, fish and seafood- as well as bacon, eggs, butter. Participants were also allowed up to 2 cups lettuce/day, 1 cup veggies per day, 4oz cheese/day. Oolichan grease (made from small smelt-like fish that are supposedly high in monounsaturated fats) was allowed and encouraged as part of the diet.

In my opinion, this is quite far from a "traditional" diet.

Food not permitted include starches like breads, pastas, rice, potatoes, as well as lactose (milk products including fresh cheese) and fructose (fruits).

From what I gathered from the documentary, adherence to the diet was determined only by interview. In fact, participants did admit to cheating, a few almost bingeing on cookies and tarts at times. One participant, a recovering alcoholic, said the cravings were so bad that he implemented the same 12-step program that he had used to deal with his alcoholism!

I noticed that some participants had cranberries and squash so it seems that the diet wasn't void of carbs... The macronutrient breakdown of the diet was not released (not sure if it was calculated).

One participant underwent open heart surgery during the study because he had 80% blockage- but he claims he had heart disease before starting the diet. Another participant dropped out because of high reflux (couldn't tolerate the high fat content).

86 people participated in the study initially but 29 dropped out. At the time of analysis, 40 people had stayed on the program for at least 4 months. These 40 people lost an average of 10kg, which is significant. Their blood pressure did increase slightly (not significantly though). Triglycerides decreased by ~20%, which was significant and probably predictable due to the drastic reduction of carbs. HDL (good cholesterol) went up a significant 17.5%, LDL (bad cholesterol) went up 2.2%, which was not significant. Total cholesterol:HDL ratio decreased 11.5% (significant). Hemoglobin A1C (average blood glucose over 3 months) also decreased.

All in all, these initial findings are promising... But what will happen in the long run? Will participants drop off the diet due to the fact that most foods are restricted? What about the long-term consequences of a high fat diet?
Physical activity did not seem to be part of the study outline, which is too bad.

What's interesting is Dr. Wortman's response to the question: Will a low-carb diet increase my risk of heart disease?

I'll copy his answer from his blog:

This is another common myth. It is based on the notion that if you eliminate carbs as an energy source you will have to increase fat intake to compensate (there is a limit to how much protein you can eat). It was thought that an increase in fat would lead to high cholesterol which is associated with heart disease. When the studies were actually done on this, however, much to everyone’s surprise, the opposite happened. People on a low-carb diet improved their cholesterol readings even when they increased their fat intake and even when their intake of saturated fat (the so-called bad fat) increased. It appears that when you body must rely on fat for energy, the saturated fat you eat gets burned up before it can cause any harm. Another factor that plays a role in heart disease is the level of inflammation in our system. If the markers of inflammation are high we recognize this as a sign of increased risk of heart disease. We commonly order a C-reactive protein test, a marker of inflammation in the blood, to assess a person’s risk. A recent study showed that people on a low-carb diet demonstrated significantly reduced inflammatory markers.

Although there haven’t been any long term studies yet to prove it, the existing science suggests that a low-carb high-fat diet may actually reduce the risk of heart disease.

I think the fact that no long-term studies have been done is important to note.
I also need to research more on the need of carbohydrates in our diet. As dietitians, we learn that our brains and bodies need glucose (from carbs) to function. If we don't get it from our diet, first our livers release its stored glucose and then our bodies break down fat and muscle that can be converted to glucose, but this results in ketones that are toxic to our bodies. Dr. Wortman states that this too is a myth. In his blog, he writes that our body is quite happy to burn ketones to meet energy needs and the amount of ketones produced isn't enough to cause any harm!

In my opinion, there must be a minimum amount of carbs that we need to get from our diet... Nonetheless, I think there is merit to the fact that a reduction in carbs can be helpful in managing diabetes and improving lipid profiles, I'm just not sure what that magic number is.
An analysis of pooled data from 13 studies has shown that a decrease of carbohydrates in the diet from 65% of calories to 35% showed improvements in Type 2 diabetes management and a 23% drop in triglycerides. However, restricted carbohydrate intake didn't result in a significant reduction in body weight.

According to Leslie Beck, RD, t
he minimum recommended daily allowance for carbohydrates is 130g per day for adults based on the minimum amount of glucose needed to feed the brain each day. This amount equals 43% of calories in a 1,200-calorie diet; 30% of calories in a 1,700-calorie diet and 24% of calories in a 2,200-calorie diet.

Sources: http://www.drjaywortman.com/blog/wordpress/about/ ; http://www.cbc.ca/thelens/bigfatdiet/wortman.html

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