[Last updated 3rd April, 2019]
Metabolic syndrome is a medical condition that’s fast becoming a worldwide epidemic.
It currently affects an estimated 25% of the world population.
If left untreated, metabolic syndrome can cause serious to life-threatening medical problems.
Fortunately, changes in diet can help prevent and treat it in many cases.
This article takes a look at the best diet for metabolic syndrome.
What is Metabolic Syndrome?
Most commonly, metabolic syndrome is characterized by having at least three of the following conditions (3):
It’s important to treat these conditions so they don’t cause significant health problems down the road.
In addition to upping your risk of diabetes and non-alcoholic fatty liver disease, metabolic syndrome doubles your risk of cardiovascular disease and increases your risk of death from any cause by 1.5 times (4).
Summary: Metabolic syndrome is a group of symptoms that increase risk for cardiovascular disease, diabetes and death. Symptoms include abdominal obesity, high blood pressure, high blood cholesterol, high triglycerides and high blood sugar.
What Causes Metabolic Syndrome?
Metabolic syndrome can be caused by any combination of genetic, lifestyle or medical factors.
Fortunately, many factors that may increase your risk—including insulin resistance, obesity and inflammation—can be modified through diet and exercise.
Insulin resistance occurs when the body’s cells become less sensitive to a hormone called insulin.
After meals, your pancreas makes insulin in response to rising blood sugar levels. Normally, insulin signals your body’s cells to pull sugar from the bloodstream. Your cells either use that sugar for energy or store it for later use.
With insulin resistance (also called impaired glucose tolerance), the body’s cells become less sensitive to the effects of insulin. Blood sugar levels increase, and so does your risk for diabetes and other complications.
Some experts argue that insulin resistance is the number one cause of metabolic syndrome, and that improving insulin sensitivity should be a top treatment priority.
Indeed, studies have linked insulin resistance to each of the components of the condition. Despite this, most organizations have excluded insulin resistance as a diagnostic criterion for metabolic syndrome. This may be partly due to the lack of a simple test for insulin resistance (5, 6, 7).
Obesity is a significant risk factor for metabolic syndrome.
However, that’s not to say that normal-weight adults aren’t at risk.
In one large study of more than 64,000 adults, metabolic syndrome was seen in up to 8% of normal-weight adults (BMI under 25), up to 32% in overweight adults (BMI 25-30), and up to 71% in obese adults (BMI greater than 30) (8).
Another large study of more than 13,000 adults found that as much as 17% of normal-weight adults had metabolic syndrome. Risk was especially high for men and women with BMI greater than 23.7 and 22.4, respectively. Researchers recommended further screening for those at the higher end of a healthy BMI range (9).
Obesity can increase health risks in and of itself. However, excessive fat tissue also increases production of certain chemicals that can be harmful in large amounts. One of these is clusterin–a protein that plays a key role in cell death. A study just last month linked high levels of clusterin to metabolic syndrome, but much more research is needed to understand this relationship (10).
People who are obese tend to have greater production of inflammatory chemicals called cytokines in the fat cells. Those with more body fat also have higher levels of C-reactive protein (CRP), which has been linked with increased cardiovascular risk.
Other risk factors for chronic inflammation include emotional stress and a Western diet (13).
Other Medical Conditions
Several chronic medical conditions can increase your risk for metabolic syndrome, including:
- Hypothyroidism: This occurs when the body doesn’t produce enough thyroid hormone.
In one large study of more than 3,900 women, 33% with hypothyroidism also had metabolic syndrome. This was significantly greater than the women with normal thyroid function (14).
- Polycystic Ovary Syndrome (PCOS): This hormonal imbalance is characterized by overproduction of male sex hormones in the ovaries.
Clusterin is a protein that’s thought to play a key role in cell death.
As is the case with cytokines and CRP, greater amounts of clusterin are seen in those who are overweight and obese. A small, recent study suggests that excessive clusterin might increase risk of metabolic syndrome (10).
This is preliminary research that requires much more follow-up. It’ll be interesting to see if any further connections are observed.
Summary: Several factors play a role in the development of metabolic syndrome, although some have been more strongly linked than others. Insulin resistance and obesity are both major risk factors that can be modified by lifestyle. Studies have also linked the condition to chronic inflammation, hypothyroidism, polycystic ovary syndrome and elevated clusterin levels.
Medical Management of Insulin Resistance
There’s no uniform treatment strategy for metabolic syndrome.
It’s more common to manage each of its five diagnostic criteria independently. This sometimes involves medications (5).
As the name suggests, insulin sensitizers make the body more sensitive to the effects of insulin.
Both Metformin and Pioglitazone have shown success at lowering blood sugar and triglycerides while increasing HDL (the good type of cholesterol). Metformin has also been shown to significantly lower BMI (5).
Interestingly, though, at least one large study found that Metformin was less effective in reducing metabolic syndrome risk than lifestyle intervention. In the same study, Metformin was no more effective than placebo among women with the condition (17).
To some degree, this may be influenced by medication dose and other factors. Your doctor can help you decide if insulin sensitizers are right for you.
Blood Pressure and Cholesterol Medications
High blood pressure is one of the most common issues among those with metabolic syndrome.
One large study estimated that nearly 28% of those with metabolic syndrome have hypertension. Doctors use several types of medication to control high blood pressure, including (18):
- Calcium channel blockers
- ACE inhibitors
Your doctor may prescribe one of these medications if diet and lifestyle changes fail to improve your blood pressure. Similarly, they may suggest statins or cholesterol absorption inhibitors to lower your cholesterol and possibly your triglycerides.
Weight Loss Drugs
Weight loss drugs aren’t a first line of treatment for metabolic syndrome.
However, since weight loss can help reverse metabolic syndrome, they’re sometimes used among patients with a BMI of 30 or greater, or a BMI as low as 27 when multiple metabolic risk factors are also present (19).
Studies have shown that certain types of weight loss drugs promote modest weight loss of about 3-5 kilograms (7-11 pounds) compared to placebo. However, they don’t guarantee success and are meant to be taken under close medical supervision.
While doctors sometimes prescribe weight loss pills and other drugs to manage metabolic syndrome, lifestyle changes can be as effective if not more so. The rest of this article will look at some of those diet changes.
Summary: Lifestyle changes can go a long way in the treatment of metabolic syndrome. However, doctors may sometimes prescribe medications, including insulin sensitizers, blood pressure medications, cholesterol medications or weight loss drugs.
The Best Diet for Metabolic Syndrome
Those with metabolic syndrome can lower their risk with any diet that promotes weight loss, though certain diets have shown to be especially helpful.
The Mediterranean Diet
The Mediterranean Diet emphasizes fruits, vegetables, whole grains, lean proteins and healthy fats.
It’s widely considered to be one of the healthiest diets. Even U.S. News and World Report named it the 2019 Best Diet Overall. It’s also been shown to help prevent and reverse metabolic syndrome.
Adopting a Mediterranean Diet can also help with treatment.
In one study, one group of 90 volunteers with metabolic syndrome received diet and exercise advice at bi-monthly visits with a nutritionist for 2 years. A second group of 90 volunteers were instructed to follow a Mediterranean Diet for 2 years that aimed to include a certain amount of fruits, vegetables, walnuts, whole grains and olive oil consumption per day.
Both groups ate 50-60% of calories from carbohydrates, 15-20% of calories from protein, and less than 30% of calories from fat.
After 2 years, the Mediterranean Diet group saw significant increases in HDL cholesterol, as well as significant improvements in BMI, waist circumference, body weight, insulin resistance, blood pressure, blood glucose, total cholesterol, triglycerides and blood markers of inflammation.
Even more impressive, nearly 49% of those in the second group were no longer considered to have metabolic syndrome at the end of the 2-year study. By contrast, 89% of volunteers in the first group still had metabolic syndrome (21).
The Mediterranean Diet may be helpful because it promotes weight loss. But, due to it being rich in antioxidants, fiber and healthy fats, it can also lower inflammation and improve endothelial function (22).
Low-carb diets are generally considered to contain fewer than 30% of calories from carbohydrates.
They’re very popular for weight loss, which may help reverse risks associated with metabolic syndrome. It’s also been suggested that low-carb diets may reverse metabolic syndrome by improving insulin sensitivity. However, the evidence is somewhat underwhelming.
Two small human studies have found only modest improvements after six months on a low-carb diet. A third, slightly larger study also found that a low-carb diet was not much more effective than a low-fat diet at improving insulin sensitivity (23, 24).
Notably, it’s possible to reap some of the metabolic benefits of low-carb diets without drastically cutting carbs. In one study of 164 adults with hypertension, each volunteer followed three separate diets for 6 weeks:
- 58% of calories from carbohydrate, 15% from protein, and 27% from fat
- 48% of calories from carbohydrate, 25% from protein, and 27% from fat
- 48% of calories from carbohydrate, 15% from protein, and 37% from fat.
(The increased fats were mostly monounsaturated, from foods like nuts, seeds, olive oil, canola oil and safflower oil.)
The higher fat diet caused significant improvements in insulin sensitivity compared to the higher carb diet. Thus, reducing daily carb intake may help reduce metabolic syndrome risk in those with cardiovascular risk factors. However, some of these benefits may be offset if the carbs are replaced with saturated fats (25).
Large studies have linked vegetarian diets to lower risk for metabolic syndrome (3).
One recent study found better insulin sensitivity in vegetarians, and especially vegans. However, no studies to our knowledge have looked at whether plant-based diets can reverse metabolic syndrome in those who already have it (26).
Still, it’s never a bad idea to incorporate more fresh fruits and vegetables in your diet—whether you’re vegetarian or not.
Intermittent fasting has become a popular diet approach in recent years.
There are a few ways to do it. Some protocols involve restricting food for several hours per day (most often, consuming all meals within eight hours). Others sharply restrict calories for several days per week.
Studies have demonstrated that it can be a powerful weight loss strategy. So, in theory, it should help with metabolic syndrome, but evidence is mixed as to whether it’s beneficial or harmful (27).
Human and animal studies have found that intermittent fasting can lower insulin resistance and diabetes risk. Rodent studies also suggest that it can improve cardiovascular risk factors, including blood pressure variability (28, 29, 30).
However, one small human study found alternate day fasting to be no more effective than a traditional low-calorie diet in terms of weight loss or insulin sensitivity (31).
Other human studies have linked three or more meals per day with better insulin sensitivity and a lower risk for metabolic syndrome. Some even suggest that intermittent fasting may worsen insulin resistance in normal weight adults (32, 33, 34, 35).
While intermittent fasting can help you lose weight, we don’t know enough about its effects on other metabolic markers to recommend it at this time.
Summary: Of the diets reported to help with metabolic syndrome, the Mediterranean Diet has shown the most promise. Lower carb diets may lower risk for those with metabolic risk factors, but only if unsaturated fats are eaten in the place of carbs. Vegetarian diets may also protect against metabolic syndrome, but we don’t know if they can treat it. Evidence is mixed as to the effects of intermittent fasting on metabolic syndrome.
Top Diet Tips for Metabolic Syndrome
There’s no one-size-fits-all diet approach for metabolic syndrome.
Of the diets that have shown success, there’s some benefit to choosing the one that is easiest for you to stick with long-term. You can also take cues from the most effective diets without strict adherence to any single plan.
Here are some of the best tips taken from the diets mentioned above:
- Limit alcohol. Alcohol is an optional part of the Mediterranean Diet. Studies suggest that small amounts of alcohol, especially red wine, may protect against metabolic syndrome. However, too much of it will actually increase your risk.There’s no need to start drinking alcohol if you don’t already. Women who currently drink should limit themselves to 20 grams, or one drink, per day. Men should stick to no more than 40 grams, or two drinks, per day (3).
- Eat a variety of fresh fruits and vegetables. Mediterranean and vegetarian diets are both abundant in colorful produce. Fresh fruits and vegetables are rich in phytochemicals and antioxidants, which help reverse cell damage and inflammation. Fill half of your plate at each meal with fruits and veggies, aiming for 5-9 servings per day.
- Limit simple sugars. Simple sugars raise your risk for obesity and diabetes and, over time, increase your odds for insulin resistance. This may account for some of the success in Mediterranean and low-carb diets. Keep sweets, white starches, sugar-sweetened drinks and other processed sugars to a minimum.
- Choose healthy fats. There’s some controversy lately over the health impacts of saturated fats. However, monounsaturated and polyunsaturated fats have been shown to protect the heart. These fats are prominent in Mediterranean and vegetarian diets. As much as possible, your dietary fats should come from nuts, seeds, olive oil, salmon, mackerel and other sources of unsaturated fats. There’s also some evidence that avocado may be beneficial for those with metabolic syndrome, but more studies are needed to confirm this (36).
- Limit sodium. Studies have consistently linked excessive dietary sodium with heart risk. Still, more than 99% of Americans consume too much of it. One recent analysis including more than 66,000 adults found a direct link between high-sodium diets and metabolic syndrome (37, 38).
It’s best to limit restaurant meals and processed foods, and avoid salting foods at the table.
- Eat high-potassium foods. Only 2% of Americans get enough potassium in their diet. Studies have linked low potassium intake to increased risk for metabolic syndrome, at least in postmenopausal women (39 , 40).
The recommendation for potassium is 4,700 milligrams per day for adults. Many fruits and vegetables are rich in potassium, which may account for some of the success of Mediterranean and vegetarian diets. High-potassium foods include baked (not fried!) potatoes, tomato sauces, beet greens and bananas.
Summary: It’s possible to improve metabolic health by picking and choosing strategies from successful diets, like the Mediterranean Diet. Be sure to eat adequate fruits and vegetables, healthy fats and potassium. Limit simple sugars, alcohol, sodium and saturated fats.
The Take-Home Message
Metabolic syndrome is a common condition that increases your risk for cardiovascular disease, diabetes and other health problems.
If left untreated, it can also increase your risk of death.
The good news is, you can do a lot to improve your health with diet alone. Mediterranean and lower carb diets may be able to reverse certain symptoms of metabolic syndrome, while a well-planned vegetarian diet may help prevent it.
In fact, you don’t even need to follow a strict diet plan as long as you’re able to follow certain strategies that can help lower your risk. Your best bet is to eat more fruits and vegetables, healthy fats and potassium and avoid sodium, alcohol, saturated fats and simple sugars.
Making these types of diet changes, and adding in regular exercise, will go a long way in preventing and treating metabolic syndrome.