Insulin Resistance in the Brain and What It Means for Dieters
Most people have been taught that increasing weight is the cause of insulin resistance, which in turn may cause an array of different health problems. That is only half true: insulin resistance may contribute to the development of obesity, and once we start gaining abdominal fat then that may indeed contribute to insulin resistance. So a vicious circle is established in which insulin resistance helps cause obesity, which in turn causes more insulin resistance.
Another thing that we have been taught for half a century that the brain is an insulin-insensitive tissue. What that means is that the uptake and use of glucose by the brain is not affected by circulating levels of glucose and insulin. That has always seemed a bit strange, because insulin is very important in cognition. Some experts believe that disturbances of insulin and closely related hormone – insulin like growth factor 1 (IGF-1) are involved in the pathogenesis of Alzheimer’s disease.
When someone is insulin resistant, they have high circulating levels of insulin, and an obvious question is whether these high insulin levels may interfere with the normal functions of the brain. This is not a new idea. It has been known for many years that high levels of triglycerides, that may be a marker for insulin resistance, may be associated with cognitive impairment in people with type 2 diabetes.
Now colleagues in London have found that people who have peripheral insulin resistance also have brain insulin resistance especially in two brain regions – the ventral striatum and prefrontal cortex – that are involved in appetite and reward.
It looks as if one of the reasons why people with insulin resistance become obese is that the normal link between the control of food intake and energy balance is broken.
This is yet more evidence that a simple diet will not work in the long term. If the problem is metabolic and involves damage to the mechanisms that control eating, the only way to help is to use a combined approach that deals not only with the composition of the diet, but the precise time when people should eat, and the psychological and social barriers that are left over from millions of years of evolution. I outline a comprehensive and highly successful weight management technique in Healing, Meaning and Purpose. Over the last few months I have had an enormous number of requests to expand that material into another book, and in between writing this blog, I am hard at work on completing a full account of exactly what we do to help people manage their weight.
Race and Diabetes
It’s another one of those, “Everyone knows that…” facts. For forty years we have all been taught that some ethnic groups are at higher risk of developing insulin resistance and type 2 diabetes mellitus. So now “everyone knows that” African Americans, Native Americans and people from the Indian sub-continent are all genetically predisposed to these medical maladies.
Now it looks as if “everyone” might have been wrong.
James Neel first proposed the theory of the “thrifty genotype” in 1962. He suggested that cycles of feast and famine early in human history created a gene that helps the body use scarce nutrients – a gene that leads to obesity and diabetes in sedentary modern populations with ready and continuous access to food.
Several months ago I pointed out some of the problems with the thrifty genotype theory, and why many of us have become more convinced about the concept of the “thrifty phenotype.” I have many friends, colleagues and former trainees who have dedicated themselves to hunting for diabetes genes. As early as the mid-1980s I was worried that they were going to vanish down a rabbit hole.
It seemed illogical that a gene or genes could “explain” an illness that was, until recently, very rare. It would have to be a gene that was somehow switched on and off by diet or some other environmental factors. It is certainly possible but seemed implausible, given that there are dozens of genes designed to control food intake and metabolism. But my friends the gene jockeys had the louder voice, and it was good for them to see what they could find. Now, twenty years later, more than 250 genes have been studied as possible causes of type 2 diabetes, but together these genes explain less than 1 percent of diabetes prevalence worldwide.
There is an interesting piece of research published in the journal Perspectives in Biology and Medicine by a team of researchers from the United States and Australia, that supports what I was saying. The study was co-authored by UC Irvine anthropologist Michael Montoya, an anthropologist at the University of California at Irvine, together with an epidemiologist and population geneticist. Together they analyzed existing genetic studies published across a variety of disciplines. The team found no evidence to support the thrifty genotype theory.
They also found that in most existing studies of the suspected genes that contribute to diabetes in ethnic minorities, researchers had failed to control for the potential impact of social and environmental factors. If those factors are taken into account, other factors – such as poverty, housing segregation or poor diet – were stronger indicators of diabetes than genes.
As Montoya said,
“Our study challenges the presumption that Native American, Mexican American, African American, Australian Aborigine, or other indigenous groups are genetically prone to diabetes because the evidence demonstrates that higher rates of diabetes across population groups can be explained by non-genetic factors alone. Our study shows that by focusing on genes, researchers miss the more significant and alterable environmental causes of diabetes.”
One of Montoya’s co-authors, Stephanie Malia Fullerton, a population geneticist and bioethicist at the University of Washington added,
“When it comes to diabetes, we’re finding that genes are no more important for ethnic minorities than for anyone else.”
This new critique of genetic and ethnic studies will need to be replicated, and it is a little bit of a surprise that such important work was published in Perspectives rather than one of the journals dedicated to epidemiology.
I have no inside knowledge about why the study was published where it was. But it often happens that it can be very difficult to get new research published if it contradicts the mainstream. There have been examples of experts squashing data that contradicts their own, but it is uncommon. Most of the time the difficulty in getting revolutionary new data published is not because of some conspiracy, but because any kind of evidence, particularly if it is radically different, attracts the most concentrated scrutiny by independent reviewers.
If this new data analysis is confirmed, it is going to mean a radical re-think about the ways in which we screen, manage and advise people from different ethnic groups.
It also confirms something that I’ve said a hundred times: Biology is Not Destiny.
Fats, Inflammation and Depression
We have talked before about the associations between inflammation and psychiatric illnesses.
There is yet more evidence in the shape of a study just published in the journal Psychosomatic Medicine. by Janice K. Kiecolt-Glaser and her colleagues from Ohio State University College of Medicine in Columbus.
The study involved 43 older adults with a mean age of 66.67 years, and the results suggests that the imbalance of omega-6 and omega-3 fatty acids in the typical American diet could be associated with the sharp increase in heart disease and depression seen over the past century. The more omega-6 fatty acids people had in their blood compared with omega-3 fatty acid levels, the higher their levels of the inflammatory mediators tumor necrosis factor-alpha and interleukin-6, and the greater the chance that they would suffer from depression. These are the same inflammatory mediators associated with insulin resistance, type 2 diabetes and coronary artery disease, all of which are more common in depression. And depression is more common in diabetes, arthritis and coronary artery disease than expected.
Our hunter-gatherer ancestors consumed two or three times as much omega-6 as omega-3, but today the average Western diet contains 15- to 17-times more omega-6 than omega-3. There were 6 individuals in the study who had been diagnosed with major depression, and they had nearly 18 times as much omega-6 as omega-3 in their blood, compared with about 13 times as much for subjects who didn’t meet the criteria for major depression.
Depressed patients also had higher levels of tumor necrosis factor alpha, interleukin-6, and other inflammatory compounds. And as levels of depressive symptoms rose, so did the omega 6 and omega 3 ratio. So it seems as if the effects of diet and depression enhance each other. People who had few depressive symptoms and/or were on a well-balanced diet had low levels of inflammation in their blood. But when they became more depressed and their diets became worse – which is very common when people are depressed – then the inflammatory mediators in the blood surged.
Omega-3 fatty acids are found in foods such as fish, flax seed oil and walnuts, while omega-6 fatty acids are found in refined vegetable oils used to make everything from margarine to baked goods and snack foods. The amount of omega-6 fatty acids in the Western diet increased sharply once refined vegetable oils became part of the average diet in the early 20th century.
Depression alone is known to increase inflammation, the researchers note in their report, while a number of studies have found omega-3 supplements prevent depression.
So this more evidence for the value of eating fatty fish like salmon, mackerel or sardines two or three times a week, but be sure to avoid fish that may contain a lot of mercury. If you add more fruits and vegetables to your diet, you will also reduce your levels of omega-6 fatty acids.
I have just finished analyzing all the new literature on using fish oils for the prevention and treatment of psychological and psychiatric problems, and I am going to post my findings in the next couple of days.
Pesticides, Weight Gain and Insulin Resistance
On this blog and in Healing, Meaning and Purpose, I have talked about some of the less well recognized contributors to obesity, including:
- Stress
- Salt
- Viruses
- Pesticides
- Intestinal bacteria
There is some new evidence from Korea published in the journal Diabetes Care, supporting the possible contribution of pesticides to insulin resistance.
People with high levels of persistent organic pollutants (POPs) in their blood were more likely to develop insulin resistance, which may lead to type 2 diabetes. Insulin resistance may also lead to obesity, hypertension and an array of other diseases. It is well recognized that increasing amounts of intra-abdominal fat may increase insulin resistance. It is less well known that this obesity is part of a viscous circle, with insulin resistance being associated with elevated insulin levels that may cause fat to be laid down throughout the body. Once the fat is laid down in the abdomen, it can break down, releasing fatty acids and triglycerides that in turn affect the breakdown of insulin by the liver and the release of insulin by the pancreas.
Previous research by the same group found a link between POPs and type 2 diabetes. This study confirms that background exposure to some POPs, chemicals such as organochlorine pesticides and polychlorinated biphenyls (PCBs), is also associated with insulin resistance among people who do not yet have diabetes.
The researchers also found that the association between organochlorine pesticides and insulin resistance became stronger as people got fatter. However, among people who had very low concentrations of pesticides in their blood, the researchers found little association between waist size and insulin resistance.
Some studies have suggested an association between background exposure to POPs and a variety of adverse health effects in humans and wildlife. POPs can be particularly problematic because they persist for long periods of time in the environment, accumulate up the food chain, and can travel great distances through the air and water. Therefore, even people and animals that live nowhere near a place where POPs are being applied often show high levels of these chemicals in their bloodstream.
An international treaty banning a dozen of the world’s most dangerous POPs has helped reduce exposures, but many harmful chemicals remain in use and even those that have been banned may linger in our environment for years to come. For example, chlordane was banned two decades ago in the United States but continues to be present at high levels in our food supply.
The researchers concluded that some POPs "may be involved in the pathogenesis of insulin resistance." They advise urgent prospective studies among those who have background exposure to POPs, which mostly comes from eating fatty animal foods. Since obesity may increase the toxicity of POPs, controlling weight could also help to reduce the impacts of these molecules.
In separate research involving mice, Frederick vom Saal from the University of Missouri in Columbia, Missouri has studied the effects of a different class of endocrine-disrupting chemicals, including bisphenol-A (BPA). Not long ago, BPA made news in San Francisco, where there was a lot of controversy over an ordinance that seeks to ban its use in children’s products. vom Saal’s most recent work was presented at the 2007 Annual Meeting of the American Association for the Advancement of Science (AAAS). He found that endocrine-disrupting chemicals cause mice to be
born at very low birth weights and then very rapidly gain abnormally
large amounts of weight: they could more than double their body weight
in just seven days. Vom Saal followed the mice as they got older and
found that these mice were obese throughout their lives. He said
studies of low-birth-weight children have shown a similar
overcompensation after birth resulting in lifelong obesity.
(Regular readers might remember the concept of the thrifty phenotype, and see how this research ties in with that concept). More research must be done to determine which chemicals cause this metabolic effect. According to vom Saal, there are approximately 55,000 manmade chemicals in the world, and 1,000 of those might fall into the category of endocrine disrupting. These chemicals are found in common products, from plastic bottles and containers to pesticides and electronics.
These chemicals are so pervasive that it is difficult to avoid them, and there is scant evidence that "detoxification" helps clear them. That being said, and depsite the lack of evidence, we recommend certified organic produce and regular mild detoxification programs, together with nutritional support and tapping therapies.
Aging and Exercise
It is a common observation that it becomes more difficult to do a lot of exercise as we get older, and the biceps no longer bulge quite as much after an hour in the gym. We have to exercise harder to get the same results.
Metabolism slows down as well, and for years it has been assumed that those events are linked: we slow our metabolism and find exercise harder because we gradually lose muscle mass.
But new research shows that it isn’t quite so simple, and the results should encourage any of us over forty to stay in the gym.
A new study published in the journal Cell Metabolism will likely help our understanding of that difficulty, as well as unlocking another of the secrets of type 2 diabetes.
As we become older, we hide more fat in our muscles and livers, and this fat has been linked to the age-related rise in insulin resistance that may go on to cause type 2 diabetes and hypertension.
A research team from the Howard Hughes Medical Institute based at Yale University School of Medicine compared the skeletal muscle of rats aged three-month-old and two-year-olds.
They found that an enzyme called AMP-activated protein kinase (AMPK) slowed down its activity in the older animals. AMPK’s role in skeletal muscle is to stimulate the body to burn off fat and to provide fuel for the cells. It does this by producing mitochondria – the power packs of the cell. So AMPK activity in our skeletal muscle does at least three things: it stimulates glucose uptake, increases fat oxidation and promotes the production of new mitochondria.
It has been known for some time that the skeletal muscles of marathon runners have a much greater mitochondrial content and a greater capacity to burn fat. This is probably linked to high levels of AMPK activity.
The animals were exposed to a chemicals that produce that produce acute or chronic stimulation of AMPK. They were also exercised and some were fed more food, each of which should stimulate the production of new mitochondria.
The researchers found that the older rats had lower AMPK activity than the younger animals. In addition, the muscle of young rats who did more exercise had double the normal AMPK activity while in older rats this effect was severely blunted.
The message is this: as we age it is not muscle mass but enzyme activity that falls first. We have to work harder when trying to maintain the same benefits from exercise as we did when we were young.
We know that loss of skeletal muscle mass and function as we age is a major problem that has a significant effect on quality of life of older people. If this study is confirmed in humans it would have enormous implications. In the older rats, the AMPK activity was almost gone, implying that no amount of exercise would bring those muscles back. But it would be good to know if we can work out some other methods for bringing those enzymes back to life.
Although the paper doesn’t mention it, there is also some evidence that AMPK activity may be important in controlling feeding behavior in the hypothalamus at the base of the brain and the “stress hormone” norepinephrine plays a critical role in the way in which exercise stimulates AMPK. As we get older we usually find that our tempers are less fiery and part of the reason for that is that we produce less norepinephrine.
Start exercising early in life, and never get out of the habit. For if you do, you might lose that AMPK activity forever.
“Wholesome physical exercise reconstitutes energy, stemming the aging process, making the body light and firm, while safeguarding against fatigue and inducing cheerfulness.”
–Sushruta Samhita (Indian Surgeon who wrote the book the Sushruta Samhita, c. 6th Century B.C.E.)
“Exercise is the chief source of improvement in our faculties.”
–Hugh Blair (Scottish Presbyterian Minister and Writer, 1718-1800)
“It is exercise alone that supports the spirits, and keeps the mind in vigor.”
Marcus Tullius Cicero (Roman Political Figure and Orator, c.106-43 B.C.E.)
Juices, Cardiovascular Disease and Cancer
There was an important study that came out a few months ago in the International Journal of Food Science and Nutrition.
Investigators from Dundee in Scotland decided to look at the health benefits of fresh fruit juice. While it is widely accepted that fruit and vegetables lower the risk of some cancers and of most cardiovascular diseases, the role of pure fruit and vegetable juices has never been clear. In fact many textbooks have said that 100 percent juices play a less significant role in reducing risk for both cancer and cardiovascular disease than whole fruits and vegetables since they contain less fiber, and it had been assumed that it was the fiber that was the key to their value.
The researchers analyzed a variety of studies that looked at risk reduction attributed to the effects of both fiber and antioxidants. They found that the positive impact offered by fruits and vegetables is derived not from just the fiber but also from antioxidants which are present in both juice and the whole fruit and vegetables. Juices are comparable in their ability to reduce cancer and cardiovascular risk compared to their whole fruit/vegetable counterparts.
This research goes a long way in demonstrating that fruit and vegetable juices may play an important role in reducing the risk of various diseases.
A study published in the American Journal of Medicine in September found that consuming a variety of 100 percent fruit and vegetable juices was associated with a reduced risk for Alzheimer’s disease. Japanese American individuals who drank three or more servings of fruit and vegetable juices per week had a 76 percent lower risk of developing Alzheimer’s disease than those who drank juice less than once per week. That finding seemed robust, even taking into account other potential variables. So I think that we may be able to add juices to our strategies for reducing the risk of developing Alzheimer’s disease as we get older.
There is another point of importance. Some of the fad diets claim that fruit juices should be avoided at all costs, since they can cause the release of insulin, and insulin is bad. Those proclamations have usually come from people with a limited background in biochemistry or metabolism. The research shows that they were not correct. The key is balance, and as part of a comprehensive nutritional approach, juicing can be very helpful.
And a final point: careful use of juices has long been one of the “secret” components of our system of weight management.
“Drinking freshly made juices and eating enough whole foods to provide adequate fiber is a sensible approach to a healthful diet.”
–Jay Kordich (American Health Expert, Author and Lecturer, 1921-)
“If people would only stop putting into their bodies the things that are creating their physical problems, and eat a predominantly raw vegetarian diet, along with raw vegetable juices, almost all physical problems would soon disappear from the face of the earth!”
–Reverend George M. Malkmus
(American Minister and Originator of the Hallelujah Diet, 1934-)
Chromium
When talking about chromium we’re not talking about that stuff that gets applied to metals to make them shiny.
For more than 20 years I’ve been interested and intrigued by its role in metabolism. This month’s issue of Harvard Men’s Health Watch highlights some of the research indicating possible links between chromium deficiency and diabetes, high cholesterol, heart disease and weight management.
The journal is only available for subscribers, but let me summarize some of the data for you.
Chromium exists in many forms and not all are either absorbed or biologically active. Antacids, phytates found in grains and tannins found in tea may all lower the absorption of chromium.
A point that always comes up when we discuss supplements is that some people will feel that recommended daily allowances are too low and that using larger – sometimes vast – amounts will achieve additional biological effects. There is some evidence that very large amounts of chromium may damage cells in tissue culture but very little evidence for chromium toxicity in humans. People probably vary greatly in their tolerance to chromium.
- Diabetes: Chromium has attracted most interest because of its action on the binding of insulin to at least one of the insulin receptors. Insulin is more effective if chromium is present. Chromium also has a positive influence on one of the glucose transporters in cultured fat cells. The effects of chromium on glucose and insulin seems to vary in different species. So it is difficult to extrapolate from an animal study to humans. In people with both the major types of diabetes, the consensus seems to be that chromium supplements containing 200-1,000 mcg chromium as chromium picolinate a day have been found to improve blood glucose control. Chromium picolinate is the most efficacious form of chromium supplementation. There is a small pilot study that found that in women with polycystic ovarian syndrome, a low dosage of chromium picolinate improved glucose tolerance, but did not help with the hormonal or ovulatory disturbances. This has just been confirmed in a study using a higher dosage (1,000 mcg/day). Based on a detailed review of the literature, the United States Food and Drug Administration (FDA) has determined that chromium – at least chromium picolinate – does not reduce the risk that you might develop insulin resistance or diabetes and the American Diabetes Association agrees that the benefit of chromium supplements has not been conclusively demonstrated.
- Cholesterol: Chromium deficient rats develop high cholesterol levels. But the evidence that chromium supplementation helps cholesterol levels in humans is thin. Chromium may also help people with diabetes to lower their cholesterol levels. The published evidence indicates that any beneficial effects of chromium on cholesterol is much smaller than the effects of diet and exercise.
- Coronary artery disease: There is a study suggesting a correlation between chromium levels and the risk of having a heart attack, with lower levels being associated with higher heart attack risk. That does not, of course, necessarily mean that taking chromium supplements will reduce the risk of a heart attack.
- Weight management: Despite all the advertisements, chromium supplements have not been shown to be effective in producing sustained weight loss.
There remains a possibility that some other form of chromium may be more effective on some of these parameters. There has recently been some interest in a product called Diachrome, that contains chromium and biotin. There have been several very interesting presentations about it at international meetings, but we need to see if the results pass peer review and replication.
A diet containing plenty of whole grains, nuts, broccoli, and green beans, should provide you with enough chromium. Chances are that taking a supplement will not cause harm and may perhaps help if you are at high risk of diabetes. But the evidence is still controversial.
I know of several other studies that are underway, and I shall report them to you as they appear.
But for now, when it comes to buying supplements, this is another one of those times that I say, “Caveat emptor!“
Leg Length and Cognitive Reserve
I recently mentioned the "Barker Hypothesis" which says that fetal malnutrition is associated with many physical problems later in life.
Well the difficulties may not only be physical.
I would like to tell you about an important concept that we call "Cognitive reserve." This can be thought of as our cognitive resilience. This first came to light almost twenty years ago when a post-mortem study of 137 elderly people was published in the Annals of Neurology, and confirmed something that we had suspected for years: there was a large discrepancy between the degree of Alzheimer’s disease neuropathology and the clinical manifestations of the disease. Some people had extensive pathology but they clinically had no or very little manifestations of the disease. The investigators also showed that these people had higher brain
weights and greater number of neurons compared with age-matched
controls. This lead to the idea that they had a greater "reserve." This is why building your brain throughout life is thought to reduce the ce of cognitive impaitrment later on.
Studies have shown that childhood cognition, educational attainment and adult occupation all independently contribute to cognitive reserve, and more recently it has been confirmed that education and the complexity of a person’s occupation may both slow the rate of decline in people who already have Alzheimer’s disease.
Although height is in part genetically determined, shorter leg length has been found to be associated with an adverse environment in early childhood. In a recent study of older Afro-Caribbean people living in London, shorter leg length was significantly associated with cognitive impairment, leading to the suggestion that shorter leg length may be a marker of early life stressors that then result in reduced cognitive reserve.
It is also worth recalling our discussion about the association between growth hormone and intelligence in children and between intelligence and head size.
And nutrition is one of the determinants of growth hormone synthesis and release.
Naturally this does not mean that less tall people will all get Alzheimer’s disease. But these observations have a number of practical consequences. They re-emphasize the importance of good nutrition during pregnancy: something that is simply not available to over a third of the world’s population. They also help us to identify some of the people who would most benefit from strategies to increase their cognitive reserve and to avoid some of the things that can strip it away from them.
Hormonal Disturbances and Bulimia
Bulimia, more accurately called bulimia nervosa, is an eating disorder that was first described by Professor Gerald Russell in 1977 whilst he worked at the Royal Free Hospital,in London in 1977.
There are five criteria that have to be met for someone to be diagnosed with bulimia nervosa:
- Recurrent episodes of binge eating. An episode of binge eating is characterized by both of the following:
- Eating, in a discrete period of time (e.g., within any two-hour period), an amount of food that is definitely larger than most people would eat during a similar period of time and under similar circumstances.
- A sense of lack of control over eating during the episode (e.g., a feeling that one cannot stop eating or control what or how much one is eating).
- Recurrent inappropriate compensatory behavior in order to prevent weight gain, such as self-induced vomiting; misuse of laxatives, diuretics or other medications; fasting; or excessive exercise.
- The binge eating and inappropriate compensatory behaviors both occur, on average, at least twice a week for three months.
- Self-evaluation is unduly influenced by body shape and weight.
- The disturbance does not occur exclusively during episodes of anorexia nervosa.
It has long been known that there can be a number of hormonal disturbances in people with both anorexia nervosa and bulimia, but it has never been clear whether they are a result of malnutrition, vomiting and/or the use of laxatives and diuretics. When we were both at the Maudsley Hospital in London, Gerald and I once spent several hours talking through the possibilities of doing some collaborative work on the hormonal problems in people with eating disorders. The list of disturbances was so long that we decided that we had other priorities.
So I am fascinated to see some new research from the Karolinska Hospital in Stockholm.
Amongst the most prominent problems in people with bulimia are menstrual irregularities and increased rates of polycystic ovarian syndrome (PCOS). A Dr Sabine Naessén studied 77 women with bulimia and 59 healthy volunteers.
As expected the women with bulimia had higher rates of menstrual disturbances, hirsutism and PCOS. And in line with previous research, levels of testosterone correlated with amounts of hirsutism.
The women with bulimia also had lower bone density, particularly if their menstrual cycles had stopped or if they had ever had anorexia nervosa.
She also found an association between two common polymorphisms in the estrogen receptor (ER) β gene and bulimia. She has speculated that this genetic variation might predispose women to the development of bulimia.
Her results suggest that some women with the condition may have too much of the male hormone testosterone. Half of the people treated for this imbalance reported less hunger, and fewer cravings for fatty and sugary foods.
This is important work. It is highly unlikely that eating disorders could ever be reduced to biochemical disturbances in the brain. There are so many environmental factors, for instance sexual abuse or other types of trauma, and even social pressure, that have been implicated in the etiology of the illness.
But the key point is this: why do some people develop an eating disorder after trauma while other do not? And why do some people develop eating disorders, even when they have never been traumatized in their lives?
The answer as always lies in the ways in which genes and the environment interact. If confirmed, this research may point the way toward some new ways of helping some people with this group of illnesses.
