Nutritional Management of Metabolic Syndrome

Metabolic Syndrome: 
More Than Just a Risk Factor for Disease

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The number of people with metabolic syndrome is increasing, yet those who have it often aren't aware of its significance.  Originally identified as Syndrome X by Dr. Gerald Reaven in the 1980s, metabolic syndrome increases risk for cardiovascular disease, heart attack, stroke, and diabetes. It is diagnosed in people who have central obesity (waist circumference >35 inches in women or >40 inches in men) and meet at least two of the following criteria as set forth by the American Heart Association:

• fasting blood glucose >100 mg/dL
• blood pressure >135/85 mm hg
• triglycerides >150 mg/dL
• HDL-C < 40 mg/dL in men or <50 mg/dL in women

The majority of people with metabolic syndrome have prediabetes, defined as fasting blood glucose between 100-125 mg/dL and/or hemoglobin A1c between 5.7-6.4%. Interestingly, people with hypertension may have better overall glycemic control as a result of producing large amounts of insulin, but they often develop heart disease at higher rates because of persistent and significant hyperinsulinemia. Unfortunately, it's easier to dismiss concerns about you're health when you're told you "only" have prediabetes.

Insulin resistance is defined as the inability of cells to respond normally to insulin, resulting in higher blood glucose and insulin levels. It's the hallmark of metabolic syndrome. Recently it has been suggested that hyperinsulinemia may be what causes insulin resistance rather than the more commonly held view that insulin resistance leads to increased insulin output and subsequent hyperinsulinemia. Regardless of which occurs first, high levels of serum insulin result in elevated blood pressure, inflammation, and high triglycerides and VLDL cholesterol -- all of which increase the risk for vascular events, i.e., heart attack and stroke. Unfortunately, most people who are diagnosed with prediabetes or metabolic syndrome don't realize that they've already sustained damage. For instance, it's estimated that 50% of people already have heart disease at the time diabetes is diagnosed.
 
Lifestyle Goals: Is Standard Advice Helpful or Harmful?  

The goals of treatment for metabolic syndrome are obvious: weight loss and improvement in blood pressure and lab values. Aside from drug therapy for lipids and blood pressure, what can be done from a nutritional standpoint? Here is the standard advice I found on many highly regarded websites, including the National Heart, Blood, and Lung Institute (NHBLI) site:

Lose Weight
A typical recommendation is to achieve and maintain a BMI of <25, which may not be possible or even desirable for everyone, particularly muscular, large-framed men. The BMI is also meaningless for assessing abdominal girth and body fat vs. muscle. For instance, a man with a BMI of 28 with little body fat and a 32-inch waist is metabolically much healthier than a small-framed man with a BMI of 24, a 38-inch waist, and a considerable amount of visceral fat around his organs. Of course, in people with metabolic syndrome abdominal obesity is a given, but the goal should be decreasing waist circumference rather than BMI.

Follow a Heart-Healthy Diet
It really shouldn't surprise me at this point that the "heart-healthy diet" -- essentially the DASH diet -- so often advised for people with metabolic syndrome isn't the one I'd recommend. From the NHBLI website:

"Fill half your plate with fruits and vegetables. A healthy diet also includes whole grains, fat-free or low-fat dairy products, and protein foods, such as lean meats, poultry without skin, seafood, processed soy products, nuts, seeds, beans, and peas."

Yes,  "processed" soy products.

So according to these recommendations, the following meal plan would be ideal:

Breakfast: 
Bowl of Raisin Bran cereal with sliced banana and skim milk
V8

Lunch:
Turkey sandwich with low fat mayo on whole grain bread, orange

Snack: 
Yoplait Light yogurt with fruit

Dinner:
Tofu, rice, and vegetables with low-sodium teriyaki sauce
Apple

This advice is being given to individuals with metabolic syndrome, who by definition have insulin resistance and hyperinsulinemia with elevated triglycerides, low HDL, and/or impaired fasting glucose. Unless carbohydrate portions are kept very small and fat is added -- neither of which is recommended on a low-fat diet -- these guidelines are likely to exacerbate rather than improve biomarkers and weight. And, let's face it, this plan doesn't sound that appetizing or satiating and would be difficult to sustain for most people.

An Enticing Alternative: Carbohydrate Restriction

On the other hand, research has demonstrated that low-carbohydrate diets do the following:

• Reduce postprandial blood glucose and insulin levels
• Result in a spontaneous decrease in appetite, which promotes weight loss, leading to lower basal insulin levels
• Decrease triglycerides
• Increase HDL-C
• Decrease blood pressure

Clearly, metabolic syndrome responds extremely well to carbohydrate restriction. Is there any other diet that has shown such impressive results? Some would argue that the Mediterranean Diet has demonstrated health benefits in this population, and there are certainly studies that support this claim. However, if large quantities of fruits, starchy vegetables, and grains are consumed, a Mediterranean diet plan can be as high in carbs as the low-fat plan listed above. Dr. Steve Parker has devised two Mediterranean-based diets that are appropriate for people with Metabolic Syndrome: the Low-Carb Mediterranean Diet and the Ketogenic Mediterranean Diet.

Here's an example of a low-carbohydrate meal plan based on Mediterranean Diet principles:

Breakfast: 
Greek yogurt with raspberries and chopped walnuts

Lunch:
Shrimp, tomatoes, and cucumbers with olive oil and basil

Snack: 
Mixed nuts or olives 

Dinner:
Steak with grilled zucchini, mushrooms, and eggplant
Strawberries with whipped cream

I think that sounds like a pretty enjoyable and sustainable way of eating.

And yet in most papers, on most websites, and among most endocrinologists, carbohydrate restriction isn't even discussed as an option for metabolic syndrome. "Lose weight" seems to be the primary directive, and the recommendation for achieving this is typically a low-fat, low-sodium, high-carb approach. Interestingly, much of the research on hyperinsulinemia and insulin resistance over the past two decades has been published in Diabetes and Diabetes Care, which are journals of the American Diabetes Association, an organization which recently changed its position statement to include low-carbohydrate diets as an option for people with diabetes and prediabetes. I hope other organizations will follow their lead and begin promoting carbohydrate restriction as an option -- or better yet, the best option -- for those with metabolic syndrome.


References:

1. Shanik MH, et al. Insulin resistance and hyperinsulinemia: Is hyperinsulinemia the cart or the horse? Diabetes Care 2008 Feb: 31 Suppl 2: S262-8
2. Reaven GM. Banting lecture 1988: Role of insulin resistance in human disease. Diabetes 1988 Dec;37(12); 1595-607  
3. McGavock JM, et al. Cardiac steatosis in diabetes mellitus. Circulation 2007 Sep 4;116(10):1170-5
4. Winhofer Y, et al. Short-term hyperinsulinemia and hyperglycemia increase myocardial lipid content in normal subjects. Diabetes 2012 May;61(5):1210-1216
5. Volek JS, Feinman RD.Carbohydrate restriction improves features of the Metabolic Syndrome. Metabolic Syndrome may be defined by the response to carbohydrate restriction. Nutr Metab(Lond) 2005 ;2:31 
6. Castorini CM, et al. The effect of Mediterranean diet on metabolic syndrome and its components. J Am Coll Cardiol 2011 Mar 15:57(11)1299-313