Are Low Carb Diets Healthy?

Written by Dr. Steve Chaney on . Posted in low carb diet

Can You Eat Low Carb & Live A Long And Healthy Life?

Author: Dr. Stephen Chaney

 

Are low carb diets healthy?

are low carb diets healthyAtkins, Paleo, Keto…It seems like everyone is following a low carb diet nowadays. They are popular, but they are also controversial. At this point you are probably wondering are low carb diets healthy and is there any evidence to support it one way or the other?  I searched the literature to find the answer to that question. The answer is:

Yes, there is evidence that some low carb diets are healthy…

…but, not for the reasons low carb enthusiasts give…

…and, not for the diets they promote.

Let me elaborate.

 

Why Are The Arguments Of Low Carb Enthusiasts Misleading?

are low carb diets healthy enthusiastMost proponents of low carb diets claim they are healthy based on improvements in blood parameters, usually things like lower triglycerides, higher HDL, lower blood glucose and insulin levels, and lower blood pressure. They sometimes claim lower LDL levels and lower levels of inflammation, although clinical studies are inconsistent for the effects of low carb diets on LDL and inflammation. They then go on to extrapolate from these data to claim their diet will reduce the risk of heart disease, diabetes, and other diseases.

These extrapolations are misleading for three reasons:

#1: Most of these comparisons are with the standard American diet. As I have said previously, almost anything is better than the standard American diet.

#2: Most of these studies are short term. The comparisons are generally made during the weight loss phase of these diets or at a time when the dieters have achieved significant weight loss. That is significant because weight loss improves all those parameters. If the comparisons were made during the maintenance phase or after most of the weight had been regained (as it usually is), the results might have been completely different.

#3: These blood parameters are imperfect indicators of disease risk. I find it particularly amusing that low carb proponents downplay the risk of saturated fats by saying that LDL and HDL cholesterol are imperfect indicators of disease risk and then use the same indicators to predict their diet will lower the risk of heart disease.

The only accurate way to determine the effect of a diet on disease risk is to conduct long term studies that measure the health outcomes of the diet. Those studies have been done, but they don’t support popular diets like Atkins, Paleo, or Keto.

 

Are Low Carb Diets Healthy and If So, Which Ones?

which low carb diets are healthyThere are, in fact, several long-term studies showing that low carb diets are healthy, but only if you ditch the animal protein and animal fats, and replace them with vegetable protein and vegetable oils.

For example, a 20-year study of 82,802 women in the Nurses’ Health Study found that women who ate a low-carbohydrate diet that was high in vegetable protein and oils had 30% lower risk of developing heart disease compared to women who ate high-carbohydrate, low-fat diets (T.L. Halton et al, New England Journal of Medicine, 355: 1991-2002, 2006). In contrast, the women who consumed a low-carbohydrate diet that was high in animal protein and fat fared no better than women consuming a high-carbohydrate, low-fat diet.

A follow-up study with the same group of women compared the effect of the same diets over a period of 20 years on the risk of developing type 2 diabetes (T.L. Halton et al, American Journal of Clinical Nutrition, 87: 339-346, 2008 ). The results were very similar. Women consuming a low-carbohydrate diet high in vegetable protein and oils had an 18% decreased risk of developing diabetes. Once again, the women consuming a low-carbohydrate diet high in animal protein and fats had just as high a risk of developing diabetes as women consuming the high-carbohydrate, low-fat diet.

This may have been because women consuming a low-carbohydrate, high animal protein and fat diet gained just as much weight over 20 years as women consuming a high-carbohydrate, low-fat diet. In contrast, women who consumed the low-carbohydrate diet high in vegetable protein and oils gained much less weight. At the end of the 20-year study, they weighed significantly less than the women in the other two groups (T.L. Halton et al, New England Journal of Medicine, 355: 1991-2002, 2006 ). This is not surprising, since we already know that vegetarians weigh less than their meat-eating friends.

However, it does run counter to what the low carb diet promoters have been telling you. They claim their diets help you lose weight. You do lose weight more rapidly on a typical low carb diet, but at the end of a year or two you end up weighing just as much as if you followed a low-fat diet (F.M. Sacks et al, New England Journal of Medicine, 360: 859-873, 2009) .  By the end of 20 years you will have gained significant weight compared to someone following a more plant-based diet (T.L. Halton et al, New England Journal of Medicine, 355: 1991-2002, 2006 ). It appears that the only low carb diet likely to give you permanent weight loss is a low carb vegetarian diet.

This is reinforced by another study showing that consumption of junk foods (potato chips and fries), sodas, processed meats, red meats, butter, sweets & desserts, and refined grains was associated with weight gain over a 4-year period (D. Mozaffarian et al, New England Journal of Medicine, 364: 2392-2404, 2011 ). In contrast, consumption of vegetables, fruits, nuts, whole grains, and yoghurt was associated with weight loss.

It’s not just women. A 20-year study of 40,475 men found that men consuming a low-carbohydrate diet high in animal protein and fat had a 37% increased risk of developing type 2 diabetes (L. de Koning et al, American Journal of Clinical Nutrition, 93: 844-850, 2011 ). In contrast, men consuming a low-carbohydrate diet high in vegetable protein and oils had a 34% decreased risk of developing type 2 diabetes.

 

Other Healthy Low Carb Diets

 

are low carb diets healthy vegetablesI have previously shared evidence that a Mediterranean diet reduces the risk of developing type 2 diabetes. Several recent studies have shown that a low-carbohydrate version of the Mediterranean diet is preferable for managing people who already have diabetes.

For example, one recent study put people who had just developed type 2 diabetes on either the low-carbohydrate Mediterranean diet or the low-fat, calorie-restrict diet usually recommended for overweight patients with diabetes (K. Esposito et al, Annals of Internal Medicine, 151: 306-314, 2009). At the end of 4 years, only 44% of the patients on the low-carbohydrate Mediterranean diet required drug treatment compared to 70% in the low-fat group.

Another entry into the low carb diet category is the eco-Atkins diet. It is a low-carbohydrate vegan diet (I find it amusing to label a diet “Atkins” when it has no meat and no saturated fat). For example, one recent study suggests it is more effective than a low-fat diet at reducing blood lipid levels and reducing blood pressure (D.J.A. Jenkins et al, Archives of Internal Medicine, 169: 1046-1054, 2009 ).

If you want to follow a low carb diet, the low carb Mediterranean and eco-Atkins diets are both healthy diets. You could create your own plant-based low carb diet, but you can find meal plans and recipes for both these diets online.

What Does This Mean For You?

Vegan, vegetarian, and primarily plant-based diets like the Mediterranean diet are all healthy diets. Long-term studies show they decrease your risk of developing heart disease, diabetes, cancer, and other diseases. Long-term studies also show that plant-based low carb diets help keep the pounds off and reduce your risk of heart disease and diabetes.

In contrast, meat-based low carb diets offer no advantage over low fat diets at keeping the pounds off or reducing the risk of heart disease or diabetes. There are no long-term studies on meat-based low carb diets and cancer risk, but we already know that red meat is a probable carcinogen. We also know that plant-based diets decrease your risk of several cancers. In short, there is no long-term evidence that the low-carb, meat-based diets decrease your risk of any disease and some evidence they may increase your risk of disease.

So, are low carb diets healthy?  Yes, if you stop eating animal protein and animal fats and make vegetable protein and oils a part of your diet.

The Bottom Line

 

  • Ignore the claims by proponents of the popular low carb diets that their diets are healthy. Those claims are based on:
    • Comparisons with the standard American diet.  Anything is better.
    • Short term studies when the participants were losing weight.  Any diet looks good during the weight loss phase.
    • Blood parameters (HDL, triglycerides, blood sugar, etc.). These are imperfect measures of long-term health outcomes.
  • Long-term (20-year) studies of the effects of low carb diets on health outcomes have been performed. Those studies show:
    • People following a meat-based low carb diet (one that focuses on animal proteins and animal fats):
      • Gained just as much weight over a 20-year period as people following a low-fat diet.
      • Had the same or greater risk of developing heart disease and diabetes as people following a low-fat diet.
    • People following a plant-based low carb diet (one that focuses on vegetable protein and vegetable oils):
      • Weighed significantly less than the other two groups at the end of 20 years.
      • Had a significantly lower risk of developing heart disease and diabetes than the other two groups.

In summary, vegan, vegetarian, and primarily plant-based diets like the Mediterranean diet are all healthy diets. Long-term studies show they decrease your risk of developing heart disease, diabetes, cancer, and other diseases. Long-term studies also show that plant-based low carb diets help keep the pounds off and reduce your risk of heart disease and diabetes.

In contrast, meat-based low carb diets offer no advantage over low fat diets at keeping the pounds off or reducing the risk of heart disease or diabetes. There are no long-term studies on meat-based low carb diets and cancer risk, but we already know that red meat is a probable carcinogen. We also know that plant-based diets decrease your risk of several cancers. In short, there is no long-term evidence that the low-carb, meat-based diets decrease your risk of any disease and some evidence they may increase your risk of disease.

For more details and the low carb diets I recommend, 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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Is Our Microbiome Affected By Exercise?

Posted November 6, 2018 by Dr. Steve Chaney

Microbiome Mysteries

Author: Dr. Stephen Chaney

is our microbiome affected by exerciseIn a recent post,  What is Your Microbiome and Why is it Important,  of “Health Tips From The Professor” I outlined how our microbiome, especially the bacteria that reside in our intestine, influences our health. That influence can be either good or bad depending on which species of bacteria populate our gut. I also discussed how the species of bacteria that populate our gut are influenced by what we eat and, in turn, influence how the foods we eat are metabolized.

I shared that there is an association between obesity and the species of bacteria that inhabit our gut. At present, this is a “chicken and egg” conundrum. We don’t know whether obesity influences the species of bacteria that inhabit our gut, or whether certain species of gut bacteria cause us to become obese.

Previous studies have shown that there is also an association between exercise and the species of bacteria that inhabit our gut. In particular, exercise is associated with an increase in bacteria that metabolize fiber in our diets to short chain fatty acids such as butyrate. That is potentially important because butyrate is a primary food source for intestinal mucosal cells (the cells that line the intestine). Butyrate helps those cells maintain the integrity of the gut barrier (which helps prevent things like leaky gut syndrome). It also has an anti-inflammatory effect on the immune cells that reside in the gut.

However, associations don’t prove cause and effect. We don’t know whether the differences in gut bacteria were caused by differences in diet or leanness in populations who exercised regularly and those who did not. This is what the present study (JM Allen et al, Medicine & Science In Sports & Exercise, 50: 747-757, 2018 ) was designed to clarify.  Is our microbiome affected by exercise?

 

How Was The Study Designed?

is our microbiome affected by exercise studyThis study was performed at the University of Illinois. Thirty-two previously sedentary subjects (average age = 28) were recruited for the study. Twenty of them were women and 12 were men. Prior to starting the study, the participants filled out a 7-day dietary record. They were asked to follow the same diet throughout the 12-week study. In addition, a dietitian designed a 3-day food menu based on their 7-day recall for the participants to follow prior to each fecal collection to determine species of gut bacteria.

The study included a two-week baseline when their baseline gut bacteria population was measured, and participants were tested for fitness. This was followed by a 6-week exercise intervention consisting of three supervised 30 to 60-minute moderate to vigorous exercise sessions per week. The exercise was adapted to the participant’s initial fitness level, and both the intensity and duration of exercise increased over the 6-week exercise intervention. Following the exercise intervention, all participants were instructed to maintain their diet and refrain from exercise for another 6 weeks. This was referred to as the “washout period.”

VO2max (a measure of fitness) was determined at baseline and at the end of the exercise intervention. Stool samples for determination of gut bacteria and concentrations of short-chain fatty acids were taken at baseline, at the end of the exercise intervention, and again after the washout period.

In short, this study divided participants into lean and obese categories and held diet constant. The only variable was the exercise component.

 

Is Our Microbiome Affected By Exercise?

is our microbiome affected by exercise fitnessThe results of the study were as follows:

  • Fitness, as assessed by VO2max, increased for all the participants, and the increase in fitness was comparable for both lean and obese subjects.
  • Exercise induced a change in the population of gut bacteria, and the change was comparable in lean and obese subjects.
  • Exercise increased fecal concentrations of butyrate and other short-chain fatty acids in the lean subjects, but not in obese subjects.
  • The exercise-induced changes in gut bacteria and short-chain fatty acid production were largely reversed once exercise training ceased.

The authors concluded: “These findings suggest that exercise training induces compositional and functional changes in the human gut microbiota that are dependent on obesity status, independent of diet, and contingent on the sustainment of exercise.” [Note: To be clear, the exercise-induced changes in both gut bacteria and short-chain fatty acid production were independent of diet and contingent on the sustainment of exercise. However, only the production of short-chain fatty acids was dependent on obesity status.]

 

What Does This Study Mean For You?

is our microbiome affected by exercise gut bacteriaThere are two important take home lessons from this study.

  • With respect to our gut bacteria, I have consistently told you that microbiome research is an emerging science. This is a small study, so you should regard it as the beginning of our understanding of the effect of exercise on our microbiome rather than conclusive by itself. It is consistent with previous studies showing an association between exercise and a potentially beneficial shift in the population of gut bacteria.

The strength of the study is that it shows that exercise-induced changes in beneficial gut bacteria are probably independent of diet. However, it is the first study to look at the interaction between obesity, exercise and gut bacteria, so I would interpret those results with caution until they have been replicated in subsequent studies.

  • With respect to exercise, this may be yet another reason to add regular physical activity to your healthy lifestyle program. We already know that exercise is important for cardiovascular health. We also know that exercise increases lean muscle mass which increases metabolic rate and helps prevent obesity. There is also excellent evidence that exercise improves mood and helps prevent cognitive decline as we age.

Exercise is also associated with decreased risk of colon cancer and irritable bowel disease. This effect of exercise has not received much attention because the mechanism of this effect is unclear. This study shows that exercise increases the fecal concentrations of butyrate and other short-chain fatty acids. Perhaps, this provides the mechanism for the interaction between exercise and intestinal health.

 

The Bottom Line

A recent study has reported that:

  • Exercise induces a change in the population of gut bacteria, and the change was comparable in lean and obese subjects.
  • Exercise causes an increase in the number of gut bacteria that produce butyrate and other short-chain fatty acids that are beneficial for gut health.
  • These effects are independent of diet, but do not appear to be independent of obesity because they were seen in lean subjects but not in obese subjects.
  • The exercise-induced changes in gut bacteria and short-chain fatty acid production are largely reversed once exercise training ceases.

The authors concluded: “These findings suggest that exercise training induces compositional and functional changes in the human gut microbiota that are dependent on obesity status, independent on diet, and contingent on the sustainment of exercise.”

For more details and my interpretation of the data, 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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