Dietary Fat, Carbohydrates and Metabolic Syndrome

 

From Fats to barbs to Metabolic SyndromeTime makes us fat. It’s not a myth, it’s a biologic fact. When we get old we get fat. In December 1863, William Banting, an English undertaker who went to great lengths to treat his own obesity, wrote in his now famous Letter on Corpulence: … For I have been generally informed that corpulence is one of the natural results of increasing years...”

Of course getting fat wouldn’t be an issue if it didn’t affect our quality of life and our risk of disease. Banting also wrote: … “Yet the evil still increased, and, like the parasite of barnacles on a ship, if it did not destroy the structure, it obstructed its fair, comfortable progress in the path of life”.

However, obesity’s association with aging does not mean that getting fat with all its dire consequences is inevitable. In fact we know that some people never get fat, and some people get fatter than others. Nonetheless, although there are genetic influences and other factors we can’t control, we have to understand that to a great extent it’s about how we live our lives.

It’s well documented that obesity is associated with increased risk of high blood pressure, lipid disorders and type 2 diabetes, the three hallmarks of metabolic syndrome. However, keep in mind that although obesity travels with these conditions, it’s not necessarily their underlying cause.

Sometimes we tend to focus too much on obesity as a problem by itself. If we look at it a bit differently, it appears that some aspects of modern lifestyle, together with a number of known and unknown environmental and genetic factors, have created a metabolic disorder with multiple consequences, one of which is obesity. Other consequences of this disorder, apart from the hallmarks of metabolic syndrome, are cardiovascular disease, non-alcoholic fatty liver disease, polycystic ovary syndrome, cancer and dementia.


Metabolic Syndrome and Insulin Resistance

If William Banting was alive today we would probably have diagnosed him with metabolic syndrome. He had no family history of obesity and did not consider himself lazy or inactive, and yet obesity crept upon him in his thirties.

The first description of metabolic syndrome can be traced back to Eskil Kylin (1889-1975), a Swedish physician and scientist who described a cluster of conditions, including high blood pressure, high blood sugar, obesity, and high levels of uric acid which can lead to gout. This was later to be named syndrome X or more commonly the metabolic syndrome.

The five conditions described below are used to define the metabolic syndrome. Three of these must be present in order to be diagnosed with the condition.

  • A large waistline.
  • A high triglyceride level in the blood.
  • A low HDL cholesterol level in the blood.
  • High blood pressure
  • Elevated blood sugar

Metabolic syndrome is not a rare disorder and its prevalence has been growing fast. It is believed that 70 million Americans suffer from this disorder.

In his Banting lecture, at the American Diabetic Association’s annual meeting in 1988, Gerald M. Reaven proposed insulin resistance as the underlying factor in metabolic syndrome. Since then it has been acknowledged that insulin resistance plays a key role and the term “insulin resistance syndrome” has been used by some specialists.

Insulin is a hormone secreted by the pancreas. It plays an important role for the metabolism of dietary carbohydrates. Insulin resistance is defined as a diminished response to a given concentration of insulin.  Most people with insulin resistance have elevated levels of insulin in their blood.

When the actions of insulin are impaired, carbohydrate metabolism becomes abnormal. This condition has been termed carbohydrate intolerance. It reflects the impaired ability of the body to metabolize carbohydrates when insulin resistance is present.

In his book, Why We Get Fat: And What to Do About It, Gary Taubes arguments that insulin plays a key role for the accumulation of fat in the body; … “First, when insulin levels are elevated, we accumulate fat in our fat tissue; when these levels fall, we liberate fat from the fat tissue and burn it for fuel”, … “Second, our insulin levels are effectively determined by the carbohydrates we eat”..

The Role of Carbs

The figure below is from a recently published paper by Richard D. Feinman and coworkers showing data from NHANES (National Health and Nutrition Examination Survey) indicating a large increase in carbohydrate as the major contributor to calorie excess in the United states from 1974-2000. The absolute amount of fat decreased for men during this period and showed only a slight increase for women.

From Fats to Carbs to Metabolic Syndrome

Macronutrient consumption during the epidemic of obesity and type 2 diabetes. Data from the National Health and Nutrition Examination Survey (NHANES) by year, and from Centers for Disease Control and Prevention. Inset: Incidence of diabetes (millions of people with diabetes by indicated year). Data from Gross LS, et al.

During the same time period, obesity increased dramatically and so did the prevalence of diabetes.

Today, 70% of adults in the US are classified as overweight or obese, as compared with 40% just 40 years ago.  Whether the relationship between increased consumption of carbohydrates, and increased obesity and diabetes is causal or not is still a matter of debate. However the lack of any relationship between total and saturated fat consumption and the prevalence of obesity and diabetes is stunning.

However, to be fair, it must be emphasized that mortality due to coronary heart disease has dropped significantly in most countries during the last 40 years. Data on incidence are harder to find, particularly in the US, but evidence from many European countries suggests that incidence has fallen as well. So, fewer people are diagnosed with coronary heart disease and fewer people are dying from it. Nonetheless, the prevalence of heart disease is still very high. The population is aging and people often live with existing heart disease for decades.

Of course the dramatic fall in mortality due to coronary heart disease is due to multiple factors. Medical and surgical therapy has improved. Studies have also shown that less smoking, lower blood cholesterol and better control of blood pressure have all contributed markedly to lower mortality. Meanwhile however, increased prevalence of obesity and diabetes are working in the opposite direction.

What Do We Do About It?

The most effective way to solve a problem is to go for its roots. However, when it comes to the obesity epidemic and metabolic syndrome it gets complicated because we still don’t know, or at least we don’t agree, on the underlying causes. There are several potential contributors, among them are increased calorie intake, changes in the composition of our diets, less physical activity and changes in gut microbiome (the bacterial flora in our gut).

In a recent overview in The Journal of the American College of Cardiology, Carl J. Lavie MD and coworkers argue that progressive declines in physical activity over five decades have primarily caused the obesity epidemic. Their research has demonstrated very marked declines in occupation related physical activity and household management energy expenditure during the last fifty years.

Following the publication of Lavie’s paper, Larry Husten wrote an article on Forbes suggesting a possible conflict of interest. Husten writes:  …”The article downplays the role of calories and diet and does not include the words “sugar”, “soda”, or “beverage”. Three of the five authors of the paper report financial relationship with Coca Cola.”

Gary Taubes argues that we don’t get fat because we overeat. He believes it comes down to hormonal imbalance; … “the stimulation of insulin secretion caused by eating easily digestible carbohydrate-rich foods: refined carbohydrates, including flour and cereal grains, starchy vegetables such as potatoes, and sugars, like sucrose (table sugar) and high fructose corn syrup. These carbohydrates literally make us fat, and by driving us to accumulate fat, they make us hungrier and they make us sedentary”.

Public health organizations and medical societies usually advocate a low-fat, high carbohydrate, energy deficient diet to manage weight.

The American Heart Association believes we should approach metabolic syndrome by reducing our weight; increasing our physical activity; eat a heart-healthy diet that’s rich in whole grains, fruits, vegetables, lean meats and fish, and low-fat or fat-free dairy products and avoid processed food, which often contains partially hydrogenated vegetable oils, and is high in salt and added sugar.

From Fats to Carbs to Metabolic Syndrome

… carbohydrate restriction appears to be an effective method to deal with lifestyle induced metabolic disease, and its consequences. However, unless medical professionals and health authorities acknowledge the potential of this approach, we can’t expect much success.

In her recently published book, The Big Fat Surprise, Nina Teicholz writes about the changes in the American diet since the first dietary guidelines were published in the 1970s: … “Since the 1970s, we have successfully increased our fruits and vegetables by 17 percent, our grains by 29 percent, and reduced the amount of fat we eat from 43 percent to 33 percent of calories“…

Teicholz then reflects on the striking increase in obesity and diabetes in the US: … “In all it’s a tragic picture for a nation that has according to the government, faithfully been following all the official dietary guidelines for so many years. If we’ve been so good, we might fairly ask, why is our health report card so bad“…

Existing evidence indicates that carbohydrate restriction positively affects most of the essential features of metabolic syndrome. Weight loss is usually achieved, waistline is reduced, blood pressure is improved, triglycerides and HDL-cholesterol improve, there will be less insulin resistance, and glucose metabolism improves.

Despite the obesity epidemic occurring right in front of our noses, there is still disagreement on its fundamental underlying causes. Consequently, experts disagree on how to deal with it. Unfortunately, public health authorities have not been able to offer much guidance. Nonetheless, looking at all the available evidence, carbohydrate restriction appears to be an effective method to deal with lifestyle induced metabolic disease, and its consequences. However, unless medical professionals and health authorities acknowledge the potential of this approach, we can’t expect much success.