Does Genetics Determine Weight?

Written by Dr. Steve Chaney on . Posted in Health Current Events, Healthy Lifestyle, Obesity

Does Genetics Cause Obesity?

Author: Dr. Stephen Chaney

Overweight & Skinny WomenIt’s frustrating. Try as hard as you might, you just can’t seem to lose weight. Even worse you suspect that your friends – and maybe your doctor – assume that you are cheating on your diet. It just doesn’t seem fair.

Perhaps there is a simple explanation. Maybe your genes are keeping you from losing weight. Does genetics determine weight?  It has been hypothesized that some of us have a “thrifty” phenotype when it comes to weight loss while others are “spendthrifts”. The theory is that people with a “thrifty” phenotype hold on to weight more tightly when they are “fasting” (i.e. trying to lose weight) and gain weight more readily when they are “feasting” (i.e. eating excess calories).

The metabolism of the “spendthrifts” is exactly the opposite. They lose weight rapidly when fasting and gain weight slowly when feasting. Those would be all of your skinny friends who just can’t seem to understand why you have such difficulty losing weight.

Those experts who favor the “thrifty” phenotype hypothesis point out that it would have provided a tremendous survival advantage in prehistoric times when food was scarce. That’s why some of those same experts think that up to 80% of the population has the “thrifty” phenotype. When you couple the thrifty phenotype with the typical American diet and lifestyle it becomes easy to understand why we have an obesity epidemic in this country.

Is the “thrifty” phenotype hypothesis true? Could it explain why you have such difficulty losing weight? A recent study suggests the answer to those two questions may be yes. I will outline the evidence below.

Then I will address what are probably the two most important questions for you: “If the thrifty phenotype hypothesis is true and you have the thrifty phenotype, are you destined to be overweight? Is there anything you can do about it?

How The Study Was Designed

medical studyThis study (Reinhardt et al, Diabetes, 64: 2859-2867, 2015) was truly a remarkable study. 15 healthy, but obese volunteers were put in a metabolic ward for a total of 11 weeks. In the metabolic ward every aspect of their metabolism was closely controlled and measured.

  • They were given diets that were precisely calibrated to provide a predetermined caloric (energy) input.
  • Urine and feces were collected and analyzed in an instrument called a bomb calorimeter to determine calorie (energy) output.
  • They were limited to primarily sedentary activity for the duration of the experiments, and the temperature of the metabolic ward was maintained constant. This eliminated variation in energy expenditures due to activity and temperature.
  • Metabolic energy expenditure was calculated by placing them in a special room designed to precisely measure oxygen consumption and CO2 production by the subjects over a 24 hour period. Don’t worry about the details. Just know that this is the gold standard for measuring energy expenditure.

Here is what the subject’s 11 weeks in the metabolic ward looked like:

  • During the first 3 weeks the subjects were provided with a diet designed with just enough calories to maintain their weight based on their weight and sex. If weight gain or loss was observed the calories were adjusted accordingly.
  • During one 24 hour period in week 3 the subjects were place on a diet that decreased their calories by 50%, (defined as “fasting” in this study) and the resulting decrease in metabolic energy expenditure was measured as described above.
  • During another 24 hour period in week 3 the subjects were place on a diet that increased their calories by 200% (defined as “overfeeding” in this study), and the resulting increase in metabolic energy expenditure was measured.
  • During the next 6 weeks the subjects were placed on calorie restricted diet that only provided 50% of the calories they needed to lose weight.
  • During the final 2 weeks the subjects were placed on a diet designed to provide the calories needed to maintain their new weight, whatever it was.

How Does Genetics Determine Weight?

do genetics cause obesityThe results of the study were quite interesting:

  • All of the subjects lost weight, but the amount of weight loss ranged from 5% to 12% of the original body weight.
  • Their starting weight did not influence their rate of weight loss during calorie restriction, but their metabolic response to fasting and overfeeding significantly affected their rate of weight loss. Specifically:
  • The subjects with the smallest decrease in energy expenditure during fasting and the largest increase in energy expenditure during overfeeding (the spendthrifts) lost significantly more weight during the 6 week caloric restriction period (what most of us call a diet).
  • The subjects with the largest decrease in energy expenditure during fasting and the smallest increase in energy expenditure during overfeeding (the thrifty) lost significantly less weight during the 6 week caloric restriction period.
  • The amount of caloric restriction needed to lose one pound of weight ranged from 1,558-2,993 depending on whether the subjects displayed the spendthrift or thrifty phenotype. That’s almost a 2-fold difference.

What Does This Study Mean For You?

life-is-sometimes-unfairLife isn’t fair. You probably already suspected that. Your skinny friends actually do have a much easier time losing weight than you do. In fact, they may be able to lose up to twice the amount of weight with exactly the same amount of caloric restriction.

However, the good news is that weight loss is possible – even for you. Everyone in the study lost weight – even those subjects with the thriftiest phenotype. So the question becomes what can you do to lose weight successfully? Here are 5 simple tips.

#1: Don’t give up. Stick with it. Pounds may come off slowly for you, but this study shows they will come off. You just have to keep the faith and be consistent.

#2: Watch what you eat very carefully. The researchers in this study controlled every morsel of food the subjects ate. People always lose weight more rapidly when they are in a metabolic ward. My recommendation is to track what you eat daily using one of the many available tracking apps.

#3: Be consistent with your exercise. The subjects in this study were not allowed to exercise, but that is one of the best ways to increase energy expenditure. Aerobic exercise gives you a small increase in energy expenditure during and immediately following the exercise. Weight bearing exercise gives a long term increase in energy expenditure because it increases muscle mass, and muscle burns calories faster than any other tissue.

#4: Choose a diet that preserves muscle mass (High Protein Diets and Weight Loss ) while you are losing weight.

#5: Avoid all those diets with herbal and pharmaceutical stimulants. They are dangerous and they may just kill you.  Check out  Are Dietary Supplements Safe.

 

The Bottom Line

A recent study (Reinhardt et al, Diabetes, 64: 2859-2867, 2015) did a very careful metabolic analysis and divided subjects into what they characterized as either a “thrifty” or “spendthrift” phenotype based on their changes in metabolic energy expenditure in response to fasting and overfeeding. They then looked at how those phenotypes affected weight loss during a 6 week period of caloric restriction. Does genetics cause obesity or help determine weight?  Here’s what they found:

  • All of the subjects lost weight, but the amount of weight loss ranged from 5% to 12% of the original body weight.
  • Their starting weight did not influence their rate of weight loss during caloric restriction, but their metabolic response to fasting and overfeeding significantly affected their rate of weight loss. Specifically:
  • The subjects with the smallest decrease in energy expenditure during fasting and the largest increase in energy expenditure during overfeeding (the spendthrifts) lost significantly more weight during the 6 week caloric restriction period (what most of us call a diet).
  • The subjects with the largest decrease in energy expenditure during fasting and the smallest increase in energy expenditure during overfeeding (the thrifty) lost significantly less weight during the 6 week caloric restriction period.
  • If you struggle to lose weight, this is a good news – bad news study.
  • The bad news is that life isn’t fair. You probably already suspected that. Your skinny friends actually do have a much easier time losing weight than you do.
  • The good news is that weight loss is possible – even for you. Everyone in the study lost weight – even those subjects with the thriftiest phenotype. So the question becomes what can you do to lose weight successfully? I’ve given you 5 simple tips in the article above.

 

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.

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Do Omega-3s Lower Blood Pressure in Young, Healthy Adults?

Posted August 14, 2018 by Dr. Steve Chaney

What Is The Omega-3 Index And Why Is It Important?

Author: Dr. Stephen Chaney

 

Do omega-3s lower blood pressure in healthy adults?

omega-3s lower blood pressure young adultsThe literature on the potential health benefits of omega-3s is very confusing. That’s because a lot of bad studies have been published. Many of them never determined the omega-3 status of their subjects prior to omega-3 supplementation. Others relied on dietary recalls of fish consumption, which can be inaccurate.

Fortunately, a much more accurate measure of omega-3 status has been developed and validated in recent years. It’s called the Omega-3 Index. Simply put, the Omega-3 Index is the percentage of EPA and DHA compared to 26 other fatty acids found in cellular membranes. Using modern technology, it can be determined from a single finger prick blood sample. It is a very accurate reflection of omega-3 intake relative to other fats in the diet over the past few months. More importantly, it is a measure of the omega-3 content of your cell membranes, which is a direct measure of your omega-3 nutritional status.

A recent extension of the Framingham Heart Study reported that participants with an Omega-3 Index >6.8% had a 39% lower risk of cardiovascular disease than those with an Omega-3 Index <4.2% (WS Harris et al, Journal of Clinical Lipidology, 12: 718-724, 2018 ). Although more work needs to be done, an Omega-3 Index of 4% or less is generally considered indicative of high cardiovascular risk, while 8% or better is considered indicative of low cardiovascular risk. For reference, the average American has an Omega-3 Index in the 4-5% range. In Japan, where fish consumption is much higher and cardiovascular risk much lower, the Omega-3 Index is in the 9-11% range.

Previous studies have suggested that omega-3 fatty acids lower blood pressure to a modest extent. Thus, it is not surprising that more recent studies have shown an inverse correlation between Omega-3 Index and blood pressure. However, those studies have been done with older populations, many of whom had already developed high blood pressure.

From a public health point of view, it is much more interesting to investigate whether it might be possible to prevent high blood pressure in older adults by optimizing omega-3 intake in a young, healthy population, most of whom had not yet developed high blood pressure. Unfortunately, there were no studies looking at that population. The current study was designed to fill that gap.

 

How Was The Study Done?

omega-3s lower blood pressure young healthy adultsThe current study (M.G. Filipovic et al, Journal of Hypertension, 36: 1548-1554, 2018 ) was based on data collected from 2036 healthy adults, aged 25-41, from Liechtenstein. They were participants in the GAPP (Genetic and Phenotypic Determinants of Blood Pressure) study. Participants were excluded from the study if they had been diagnosed with high blood pressure and were taking medication to lower their blood pressure. They were also excluded if they had heart disease, chronic kidney disease, other severe illnesses, obesity, sleep apnea, or daily use of non-steroidal anti-inflammatory medications.

Blood samples were collected at the time of their enrollment in the study and frozen for subsequent determination of Omega-3 Index. Blood pressure was also measured at their time of enrollment in two different ways. The first was a standard blood pressure measurement in a doctor’s office.

For the second measurement they were given a wearable blood pressure monitor that recorded their blood pressure over 24 hours every 15 minutes during the day and every 30 minutes while they were sleeping. This is considered more accurate than a resting blood pressure measurement in a doctor’s office because it records the variation in blood pressure, while you are sleeping, while you are exercising, and while you go about your everyday activities.

 

Do Omega-3s Lower Blood Pressure In Young, Healthy Adults?

omega-3s lower blood pressure young adults equipmentNone of the participants in the study had significantly elevated blood pressure. The mean systolic and diastolic office blood pressures were 120±13 and 78±9 respectively. The average Omega-3 Index in this population was 4.6%, which is similar to the average Omega-3 Index in the United States.

When they compared the group with the highest Omega-3 Index (average = 5.8%) with the group with the lowest Omega-3 Index (average = 4.6%):

  • The office measurement of systolic and diastolic blood pressure was decreased by 3.3% and 2.6% respectively
  • While those numbers appear small, the differences were highly significant.
  • The 24-hour blood pressure measurements showed a similar decrease.
  • Blood pressure measurements decreased linearly with increasing Omega-3 Index. [In studies of this kind, a linear dose-response is considered an internal validation of the differences observed between the group with the highest Omega-3 Index and the group with the lowest Omega-3 Index.]

The authors concluded: “A higher Omega-3 Index is associated with statistically significant, clinically relevant, lower systolic and diastolic blood pressure in normotensive, young and healthy individuals. Diets rich omega-3 fatty acids may be a strategy for primary prevention of hypertension.”

 

What Does This Mean For You?

omega-3s lower blood pressure young adults questionPerhaps I should first comment on the significance of the relatively small decrease in blood pressure observed in this study.

  • These were young adults, all of whom had normal or near normal blood pressure.
  • The difference in Omega-3 Index was rather small (5.8% to 4.6%). None of the participants in the study were at the 8% or above that is considered optimal.
  • Liechtenstein is a small country located between Switzerland and Spain. Fish consumption is low and omega-3 supplement consumption is rare.

Under these conditions, even a small, but statistically significant, decrease in blood pressure is remarkable.

We should think of this study as the start of the investigation of the relationship between omega-3 status and blood pressure. Its weakness is that it only shows an association between high Omega-3 Index and low blood pressure. It does not prove cause and effect.

Its strength is that it is consistent with many other studies showing omega-3 fatty acids lower blood pressure. Furthermore, it suggests that the effect of omega-3s on blood pressure may also be seen in young, healthy adults who have not yet developed high blood pressure.

Finally, the authors suggested that a diet rich in omega-3s might reduce the incidence of high blood pressure by slowing the age-related increase in blood pressure that most Americans experience. This idea is logical, but speculative at present.

However, the GAPP study is designed to provide the answer to that question. It is a long-term study with follow-up examinations scheduled every 3-5 years. It will be interesting to see whether the author’s prediction holds true, and a higher Omega-3 Index is associated with a slower increase in blood pressure as the participants age.

 

Why Is The Omega-3 Index Important?

 

The authors of this study said: “The Omega-3 Index is very robust to short-term intake of omega-3 fatty acids and reliably reflects an individual’s long-term omega-3 status and tissue omega-3 content. Therefore, the Omega-3 Index has the potential to become a cardiovascular risk factor as much as the HbA1c is for people with diabetes…” That is a bit of an overstatement. HbA1c is a measure of disease progression for diabetes because it is a direct measure of blood sugar control.

In contrast, Omega-3 Index is merely a risk factor for cardiovascular disease. However, if it is further validated by future studies, it is likely to be as important for predicting cardiovascular risk as are cholesterol levels and markers of inflammation.

However, to me the most important role of Omega-3 Index is in the design of future clinical studies. If anyone really wants to determine whether omega-3 supplementation reduces cardiovascular risk, high blood pressure, diabetes or any other health outcome they should:

  • Start with a population group with an Omega-3 Index in the deficient (4-5%) range.
  • Supplement with omega-3 fatty acids in a double blind, placebo-controlled manner.
  • Show that supplementation brought participants up to an optimal Omega-3 Index of 8% or greater.
  • Look at health outcomes such as heart attacks, cardiovascular deaths, hypertension, stroke, or depression.
  • Continue the study long enough for the beneficial effects of omega-3 supplementation to be measurable. For cardiovascular outcomes the American Heart Association has stated that at least two years are required to obtain meaningful results.

These are the kind of experiments that will be required to give definitive, reproducible results and resolve the confusion about the health effects of omega-3 fatty acids.

 

The Bottom Line

 

An accurate measure of omega-3 status has been developed and validated in recent years. It’s called the Omega-3 Index. Simply put, the Omega-3 Index is the percentage of EPA and DHA compared to 26 other fatty acids found in cellular membranes.

Although more work needs to be done, an Omega-3 Index of 4% or less is generally considered indicative of high cardiovascular risk while 8% or better is considered indicative of low cardiovascular risk.

Previous studies have shown an inverse correlation between Omega-3 Index and blood pressure. However, these studies have been done with older populations, many of whom had already developed high blood pressure.

From a public health point of view, it is much more interesting to investigate whether it might be possible to prevent high blood pressure in older adults by optimizing omega-3 intake in a young, healthy population, most of whom had not yet developed high blood pressure. Until now, there have been no studies looking at that population.

The study described in this article was designed to fill that gap. The participants in this study were ages 25-41, were healthy, and none of them had elevated blood pressure.

When the group with the highest Omega-3 Index (average = 5.8%) was compared with the group with the lowest Omega-3 Index (average = 4.6%):

  • Both systolic and diastolic blood pressure were decreased
  • Blood pressure measurements decreased linearly with increasing Omega-3 Index.

The authors concluded: “A higher Omega-3 Index is associated with statistically significant, clinically relevant, lower systolic and diastolic blood pressure in normotensive, young and healthy individuals. Diets rich omega-3 fatty acids may be a strategy for primary prevention of hypertension.”

Let me translate that last sentence into plain English for you. The authors were saying that optimizing omega-3 intake in young adults may slow the age-related increase in blood pressure and reduce the risk of them developing high blood pressure as they age. This may begin to answer the question “Do omega-3s lower blood pressure in young, healthy adults?”

Or even more simply put: Aging is inevitable. Becoming unhealthy is not.

For more details, read the article above.

 

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.

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