Tuesday, November 13, 2018

Can your genes predict the best weight loss diet for you?


The Study
It has been hypothesized that your genetic makeup can predict which weight loss strategy will be the most effective for you. In this interesting study, 609 adults were randomized to either a low-fat or low-carb diet for 12 months. Previous research has suggested that a certain genotype that impacts carbohydrate metabolism may help a person be more successful with a low-carb diet. Similarly, another genotype that influences fat metabolism has been identified that may make a person more successful on a low-fat diet. Before the trial began, subjects were tested for this low-fat or low-carb response gene sequence.  

Among the participants randomized to the low-fat diet, 130 had the low-fat gene and 83 had the low-carb gene. Among the participants randomized to the low-carb diet, 114 had the low-fat gene and 97 had the low-carb gene. By the end of the 12 month follow-up, there were no differences in weight lost between the two groups and neither the low-fat or low-carb genotype predicted weight loss success.
Journal of the American Medical Association 2018; 319:667.

Take Home Message
Although the idea that our genes can tell us what weight loss diet is best for us is intriguing, this study does not provide evidence that this is the case. More research is needed before we can definitively answer this question.


Dietary Insulin And Colon Cancer


The Study
In this investigation, Harvard researchers created a dietary scoring system of foods that promote a high insulin response. They called it the Empirical Dietary Index for Hyperinsulinemia (EDIH). This is different than the glycemic index, which focuses on the blood sugar effects of carbohydrate containing foods. This index includes all foods that spike insulin after consumption. 

The food groups that contributed to a high EDIH score include red meat, low energy soda, cream soups, processed meats, margarine, poultry, French fries, fish, sugar sweetened beverages, tomatoes, low fat dairy and eggs.

The food groups that contributed to a low EDIH score included wine, coffee, fruit, high fat dairy products and green leafy vegetables.

Over 120,000 men and women from the Nurses’ Health Study and the Health Professional Follow-up Study had an EDIH score calculated for their diet and were followed for 26 years. Subjects with the greatest EDIH score had a statistically significant 26% higher risk of colon cancer when compared to subjects with the lowest EDIH score. American Journal of Clinical Nutrition 2018; 108:363-70.

Take Home Message
When choosing a diet to promote weight loss, you always want to look at the long-term health effects of the diet as well.   

The EDIH score takes the idea of the glycemic index a step further. The GI focuses on the blood sugar effects of carbohydrate foods. The EDIH score includes any food that increases insulin. A lot of these foods are proteins. Many popular current diets are really high in animal protein, and this study makes you think twice about them. 

As far as mechanisms go, it is thought that very high levels of insulin, and insulin derived growth hormone may be carcinogenic. 

In addition to keeping your glycemic index low, it is a good idea to go easy on the animal proteins. It is particularly important to limit red meat and processed meats. It is also a good idea to substitute vegetable proteins such as beans, nuts, whole grains and legumes for animal proteins whenever possible.


Carbohydrate Consumption And Mortality


Carbohydrate consumption has been a hot button issue in the field of nutrition for decades. The type and amount of carbohydrate we should be including in our diets is the subject of intense debate in both the research and weight loss communities. This is a subject that is near and dear to my own heart since carbohydrate metabolism was the subject of my own doctoral research. A new study has been published on this topic that is well done and very important.

The Article
This investigation actually consists of two separate studies (Reference 1). The first is a prospective cohort study using the ARIC cohort (The Atherosclerosis Risk in Communities). The second is a meta-analysis including 7 separate studies.

Results
Prospective Cohort Study in the ARIC Cohort
Over 15,000 adults aged 45-64 years in 4 U.S. communities had their diet assessed by means of a food frequency questionnaire and were followed for 25 years. Subjects who consumed 50-55% of their calories as carbohydrate had the lowest mortality rate. Subjects who ate more or less carbohydrate had an increased mortality risk.

-A 50 year old subject consuming less than 30% of calories as carbohydrate would have a projected life expectancy of 29.1 years.

- A 50 year old subject consuming 50-55% of calories as carbohydrate would have a projected life expectancy of 33.1 years.

A 50 year old subject consuming greater than 65% of calories as carbohydrate would have a projected life expectancy of 32 years.

Meta-analysis
The meta-analysis consisted of 8 separate studies with a total of 432,179 subjects and showed a similar result. There was an increased risk of mortality with both a low and high carbohydrate intake when compared to a moderate carbohydrate intake.

Subjects consuming less than 40% of calories as carbohydrate had a statistically significant 20% higher risk of mortality.

Subjects consuming greater than 70% of calories as carbohydrate had a statistically significant 23% higher risk of mortality.

Substituting animal fat and protein for carbohydrate resulted in an increased risk of mortality.

Substituting vegetable fat and protein for carbohydrate resulted in a decreased risk of mortality.

Conclusions And Recommendations
Many people manipulate their carbohydrate consumption in an effort to lose weight. It is really important to examine what effect these weight loss diets may have on long term health. My professional goal has always been to provide a strategy that helps my client lose weight effectively, while improving overall health and decreasing risk of chronic disease. 

This study sheds some light on the long-term health effects of diets that severely manipulate carbohydrate consumption. The mechanisms are pretty straight forward. A low carb diet will generally include less healthy foods such as fruits, vegetables and whole grains and higher amounts of red meat and saturated fat. This results in fewer vitamins, minerals, fiber and cancer fighting phytochemicals. This eating pattern likely results in higher levels of oxidative stress, inflammation and biological aging.

On the other hand, diets very high in carbohydrates tend to include too many refined carbohydrates and not enough healthy vegetable fat. This results in a much higher dietary glycemic load, which has been associated with many negative health outcomes.

Here is what we learn from this important study:
1) Going very low carb is probably not a great idea.

2) Going very high carb is probably not a great idea.

3) Stay in the mid carb range, which is around 50-55% of calories.

4) The quality of carbohydrates consumed is of the utmost importance. Focus on low glycemic carbs such as fruits, vegetables, legumes and whole grains.

5) The majority of your fat should be vegetable fats such as nuts, avocado, nut butters, seeds and healthy vegetable oils such as olive oil and canola oil.

6) Minimize sources of protein that are high in saturated fat, especially red meat and processed meats like bacon, sausage, pepperoni, hot dogs, etc. 

References
1) Seidelmann SB, et al. Dietary carbohydrate intake and mortality; a prospective cohort study and meta-analysis. Lancet Public Health 2018; 9:pe419-e428.

Thursday, September 13, 2018

Can I Eat Nuts If I Am Trying To Lose Weight?


Nuts absolutely fit into a weight loss diet.  Here are some of the great things about them:

-They are low glycemic load and therefore are very easy on the blood sugar.

-They contain a healthy source of protein.

-They contain fiber.

-They contain vitamins.

-They contain minerals.

-They contain very healthy sources of fat.

High nut consumption has been associated with a lower risk of heart disease and type 2 diabetes in Harvard prospective cohort studies (Reference 1 and 2).  Now nuts do contain a lot of calories, so you have to be a little careful with your portions.

However, an analysis in the Nurse Health Study showed that women who ate nuts more frequently actually had a reduced risk of obesity compared to women ate them less often (Reference 3).  Feel free to include nuts regularly in your diet, even if you are trying to lose weight.

References
1) Hu FB et al. Frequent nut consumption and risk of coronary heart disease in women: prospective cohort study. British Medical Journal 1998; 317:1341-45.

2) Jiang R, et al. Nut and peanut butter consumption and risk of type 2 diabetes. Journal of the American Medical Association 2002; 288:2554-60.

3) Bes-Rastrollo M, et al. Prospective study of nut consumption, long term weight change and obesity risk in women. American Journal of Clinical Nutrition 2009; 89:1913-19.


Is Sugar Addiction Genetic?


The Study
In the last few years, evidence suggests that sugar is addictive, similar to alcohol or tobacco. A recent publication tested the hypothesis that sugar addiction is genetic. In this investigation, 108 healthy weight adolescents were given milkshakes with varying sugar contents while undergoing a functional brain MRI. If both parents were overweight, the subject was considered at high risk of becoming overweight. If neither or just one parent was overweight, the subject was considered to be at low risk.

Fifty-three of the subjects were considered high risk and fifty-five were considered low risk. When compared to the low risk subjects, the high risk adolescents showed a significantly greater striatal, gustatory and somatosensory response to the high sugar milk shake. These areas of the brain have been shown to be associated with reward and addiction. American Journal of Clinical Nutrition 2018; 107:859.

Take Home Message
This study tells us several things:
1) Sugar consumption appears to fire up the regions of the brain associated with reward and addiction. The research that this may be the case has been building for some time.

2) The authors conclude that sugar may be more responsible for habitual overeating than other dietary components, such as dietary fat. I agree with them.

3) There may be a genetic component to sugar addiction.

I have observed the addictive nature of sugar for years. In most people that I have worked with, if they have a little sugar, they want more and more. The best bet is to just swear off sugar entirely. Although this is really hard at first, after a few weeks, you’ll hardly miss it.  For most of us, limiting sugar to just a few servings a week is like telling an alcoholic to just have a few drinks per week. It simply doesn’t work. 


Carbohydrate Quality And Osteoporosis


The Study
Osteoporosis is a disease that reduces bone strength and markedly increases risk of fracture. It can dramatically reduce quality of life and ability to function as we age. In this study, 870 subjects from the Spanish based PREDIMED cohort had their glycemic index and glycemic load measured by food frequency questionnaire annually for 9 years. When compared to subjects with the lowest glycemic index, subjects with the highest glycemic index had an 80% higher risk of osteoporotic fracture. When compared to subjects with the lowest glycemic load, subjects with the highest glycemic load had a 320% higher risk of osteoporotic fracture. American Journal of Clinical Nutrition 2018; 107:1035.

Take Home Message
We can add osteoporosis to the growing list of diseases that may occur when we focus on the wrong carbohydrates. The authors believed that the increased blood sugars associated with high glycemic carbs explained the higher risk of osteoporosis through several potential mechanisms:

-Increased inflammation.
-Increased oxidative stress.
-A decrease in osteoblast activity.
-Acidosis.
-Inhibition of genes involved in osteoblast differentiation.
-An increased excretion of calcium in the urine.

To reduce the glycemic index and glycemic load of your diet, strictly limit refined carbohydrates such as bread, pasta, white rice and sugar. Focus on fruits, vegetables, legumes and whole grains such as oatmeal, brown rice and quinoa. You also don’t want to go too heavy on the carbs. Shoot for about 45-50% of your daily calories as carbohydrate.


Lifestyle Factors And Life Expectancy


A new study was recently published that is so compelling that it deserves its very own feature article. The study is titled “Impact of healthy lifestyle factors on life expectancies in the US population” and it was published in the journal Circulation. The authors of this investigation are the very best of the Harvard School of Public Health’s Department of Nutrition faculty, which includes Dr. Walter Willett, Dr. Frank Hu and Dr. Meir Stampfer (Reference 1).

Most nutrition research focuses on a very specific aspect of lifestyle and its impact on health. For example, “eating red meat increases incidence of colon cancer” or “eating oatmeal decreases serum cholesterol”. What makes this study so interesting is that several lifestyle behaviors are combined so we can see their cumulative impact on health.

The Article
This investigation used subjects from both The Nurses’ Health Study and The Health Professional Follow-up Study for a total of 123,219 men and women. The researchers created 5 lifestyle factors and scored each subject on how well they followed the behavior. Here is the scoring system:

1) Smoking: If the subject never smoked they received a score of 1. If they were a current smoker or had smoked in the past, they received a score of 0.

2) Physical Activity: If the subject engaged in 30 minutes or more of moderate to vigorous physical activity each day they received a score of 1. If they did less than this, they received a score of 0.

3) Alcohol Consumption: Low risk was considered an alcohol consumption of 5 to 15 grams per day for women (which equals 2.5-7.5 drinks per week) and 5 to 30 grams per day for men (which equals 2.5-14 drinks per week). If the subject’s alcohol consumption was in this range, they received a score of 1, if not they received a score of 0.

4) Body Mass Index: Low risk was considered a BMI between 18.5-24.9. If the subject’s BMI was in this range, they received a score of 1, if not they received a score of 0.

5) Diet: Subjects received a score of 1 for this variable if their diet was in the top 40% of the cohort distribution for the Alternate Healthy Eating Index. This diet score is based on a high consumption of vegetables, fruits, nuts, whole grains, polyunsaturated fats and long chain omega 3 fatty acids and a low intake of red and processed meats, sugar sweetened beverages, trans fat and sodium.

Each subject was given a score for the 5 lifestyle factors. A perfect lifestyle would be a score of “5”, while adhering to none of the lifestyle factors would yield a score of “0”.  Subjects were followed for up to 34 years.

Results
When comparing subjects who followed all 5 factors to subjects following none:

-Risk of all-cause mortality was 74% lower in subjects that followed all 5 factors.

-Risk of death from cancer was 65% lower in subjects that followed all 5 factors.

-Risk of death from cardiovascular disease was 82% lower in subjects that followed all 5 factors.

Starting at age 50, women following all 5 factors could expect to live another 43.1 years, while women following none of the factors could expect to live another 29 years.

Starting at age 50, men following all 5 factors could expect to live another 37.6 years, while men following none of the factors could expect to live another 25.5 years

The researchers ran an additional analysis with a stricter criterion for the lifestyle score.

Body mass index: A score of 1 was given to those with a BMI between 18.5 and 22.9.

Physical Activity: A score of 1 was given to those exercising more than 52 minutes per day.

Diet: A score of 5 was given to those in the top 20% of the distribution for the Alternate Healthy Eating Index.

The scoring for smoking and alcohol consumption were kept the same.

Women who followed this expanded score lived 20.5 years longer than those that followed none of the lifestyle factors. For men, the number was 19.6 years.

Conclusions And Recommendations
These results are truly remarkable. To think that by living a healthy lifestyle you could add up to 20 years to your life is amazing. The coolest part is that this study does not take into account quality of life, which is much higher if you follow these habits. If you are able to hit all 5 of these behaviors consistently, you will notice significant and positive changes in your energy, mood, immune system, confidence, mental focus/performance and how you handle stress. 

The take home message on this is one is simple. Go through each of the 5 lifestyle factors and give yourself a score. If you are at 5, you are all set and keep up the good work. If you are hitting less than 5, do your best to work towards a perfect score. Will it be easy to attain all 5 of these? Probably not. However, the effort you put into a healthy lifestyle is paid back to you many times over. It all begins with making your health a priority.

References
1) Li Y, et al. Impact of healthy lifestyle factors on life expectancies in the U.S. population Circulation 2018 DOI: 10.1161/CIRCULATIONAHA.117.032047.