Insulin Resistance Syndrome

The right diet is the key to managing many diseases and to improving general quality of life. For this condition, scientific research has found benefit in the following healthy eating tips.

• High-Protein Diet

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  High-proteins diets may help people with metabolic syndrome achieve weight loss, and some evidence suggests plant protein may have more positive effects on metabolism than animal protein.

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  High-Protein Diet

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  Research into the effects of high-protein diets on metabolic health has yielded inconsistent evidence.⁸⁸ A study using data from over 3,000 middle-aged adults examined the relationship between protein intake and cardiac and metabolic risk factors. The analysis found those with higher protein intake, compared to those with lower protein intake, had better systolic (but not diastolic) blood pressure but worse blood glucose levels after 20 years of monitoring; no relationship was seen between protein intake and changes in body weight, waist circumference, cholesterol levels, or triglyceride levels. When protein source was considered, higher plant protein intake was associated with better blood glucose levels and waist circumference, but higher animal protein intake was associated with worsening of both of these aspects of metabolic syndrome.⁸⁹ In a study in people with metabolic syndrome, eating a high-protein, reduced-calorie diet led to more weight loss than a standard reduced-calorie diet after six months; however, there were no other differences between the diets on aspects of metabolic syndrome.⁹⁰ Another dietary intervention trial compared the effects of high-plant protein, high-animal protein, and normal-protein healthy diets in 62 overweight adults with metabolic syndrome during a 23-week weight loss program. All of the diet interventions led to similar weight loss and improvements in metabolic syndrome, with no significant differences between groups.⁹¹

• Low-Glycemic Index Diet

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  Avoiding high-glycemic index foods, which are most often refined starches and sugary foods, may help protect metabolic health, but is not sufficient to treat metabolic syndrome.

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  Low-Glycemic Index Diet

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  The glycemic index is a system that rates foods by their blood glucose-raising effect relative to an equal carbohydrate portion from a reference food, while the glycemic load takes into account the carbohydrate content of a typical serving (quantity) as well as the blood glucose-raising potential (quality). While a diet rich in high-glycemic index foods has been found to worsen blood glucose control, insulin sensitivity, lipid levels, and obesity, it is unclear whether low-glycemic index and low-glycemic load diet interventions are helpful in people with metabolic syndrome.⁹² A meta-analysis of studies found higher amounts of high-glycemic index foods in the diet corresponded with increased risk of metabolic syndrome, but a high-glycemic load diet was not correlated with risk.⁹³ Another meta-analysis found low-glycemic index and load diets had no impact on cardiovascular or all-cause mortality in men, and only a low-glycemic index diet appeared to have a protective effect in women.⁹⁴

• Mediterranean Diet

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  A Mediterranean dietary pattern has been shown in multiple studies to aid in the management of metabolic syndrome and prevention of type 2 diabetes and cardiovascular disease.

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  Mediterranean Diet

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  The Mediterranean diet emphasizes fruits, vegetables, whole grains, legumes, nuts, fish, and olive oil, and includes small amounts of dairy products, poultry, and red wine. Switching to a Mediterranean-type diet was found to improve the nutrient density of the diet in a trial with more than 5,700 participants affected by metabolic syndrome.⁹⁵ Adherence to a Mediterranean dietary pattern has been found in multiple observational studies, clinical trials, and research reviews to improve health in people with metabolic syndrome and reduce the risk of metabolic disease in healthy individuals.^96,97,98 Furthermore, comparison trials show it is more effective than standard diet recommendations and low-fat diet for reducing signs of metabolic syndrome.^99,100

  While including foods that are part of the Mediterranean diet can improve metabolic health, there may be other aspects of food choice that also influence the diet’s impact. For example, one interesting study that included a group of participants with strong adherence to Mediterranean diet found those who ate more locally sourced food were less likely to have metabolic syndrome compared to those who ate more food from farther away.¹⁰¹

• Low-Fat

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  In general, a low-fat diet is not indicated for prevention or treatment of metabolic syndrome; instead, modest consumption of a variety of fats, with emphasis on polyunsaturated and monounsaturated fats, appears to improve metabolic health.

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  Low-Fat

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  It is a long-held assumption that a high-fat diet can induce obesity and metabolic dysregulation; however, a large body of evidence now shows that replacing carbohydrate calories with fat of any type can lower triglyceride levels and raise HDL-cholesterol levels, and consuming poly- and mono-unsaturated fats (but not saturated fats) may improve glucose metabolism.¹⁰² A study that included over 6,000 participants found those with the highest intakes of total fat, saturated fat, and monounsaturated fat had higher blood glucose levels than those with lower intakes. Unexpectedly, those with the highest saturated fat intake had lower triglyceride levels.¹⁰³ Another study from Brasil with 9,835 participants found high intake of saturated fat from dairy products appeared to protect against metabolic syndrome, contributing to speculation that not all saturated fats are equal in their health effects.^104,105

  Polyunsaturated omega-3 fats from fish have been suggested to have a protective role: a study compared diet to incidence of metabolic syndrome in 4,356 young adults during 25 years of observation and found high consumption of omega-3 fatty acids from fish reduced the likelihood of developing metabolic syndrome.¹⁰⁶

• Low-Carbohydrate

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  Low- and very low-carbohydrate diets can help normalize metabolic parameters, but the long-term safety of a ketogenic diet is not known.

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  Low-Carbohydrate

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  Increased carbohydrate intake, as a percentage of total calorie intake, has been clearly associated with higher risk of metabolic syndrome.¹⁰⁷ However, one study that included 164 people with type 2 diabetes noted high carbohydrate intake was only related to metabolic syndrome, and in particular to high triglyceride and low HDL-cholesterol levels, in those with low fiber intake, suggesting carbohydrate quality, as much as quantity, impacts metabolic health.¹⁰⁸ In a clinical trial in subjects with obesity and metabolic syndrome, a four-week, low-carbohydrate, high-fat, weight maintenance diet intervention was found to improve some features of metabolic syndrome (triglyceride and cholesterol levels) more than moderate- or high-carbohydrate weight maintenance diets.¹⁰⁹

  A very low-carbohydrate diet, in which only 5%–10% of calorie intake is from carbohydrates, induces a physiologic state called ketosis, marked by high levels of ketones (products of fat metabolism). A therapeutic ketogenic diet includes 20–50 grams of carbohydrate per day, 1–1.5 grams of protein per kilogram of body weight, and unlimited fat. The ketogenic diet has been found to improve aspects of metabolic syndrome, including insulin resistance, blood glucose control, waist circumference, cholesterol and triglyceride levels, and blood pressure, as well as levels of inflammatory markers.¹¹⁰ One uncontrolled trial in 377 participants found a ketogenic diet reduced body weight, waist circumference, fat mass, and systolic blood pressure within 12 weeks and the benefits were maintained over one year of monitoring.¹¹¹

  Little is known about the long-term effects of such a low-carbohydrate diet, which is notably low in prebiotic fibers needed to maintain a balanced gut microbiome, on health outcomes and mortality.^112,113,114 A pooled analysis of clinical findings reported people eating low-carbohydrate diets have a substantially higher mortality rate.¹¹⁵ In addition, a study that followed more than 15,000 American adults for about 25 years found the lowest mortality rate occurred in those with moderate carbohydrate intake (50%–55% of calorie intake), while both low (<40%) and high (>70%) carbohydrate intakes were associated with higher mortality. This study further noted that, among those with low carbohydrate intake, only those who replaced carbohydrates with protein and fat from animal sources experienced an increase in mortality; instead, those who replaced carbohydrates with protein and fat from plant sources had a lower mortality compared to moderate carbohydrate consumers.¹¹⁶