Romanesco Broccoli in a Beaker

One of the most consistent themes of nutrition science is that vitamin supplements (pills, powders, liquids, etc.) are almost never able to mimic the beneficial effects of foods that contain the same vitamins. Now new evidence suggests that high doses of these antioxidant supplements–but not whole foods containing them–may actually block the beneficial effects of exercise on insulin sensitivity and metabolism.

Exercise has countless benefits for people of all levels of fitness. One of the most important of these is its ability to improve insulin sensitivity and increase metabolism. For this reason, exercise is considered among the most effective ways to protect against type 2 diabetes.

One of the byproducts of exercise, however, is the production of free radicals that results from the breakdown of oxygen in the muscles. These reactive oxygen molecules can damage cells and DNA, and are implicated in many chronic diseases. Since antioxidants can easily neutralize these reactive oxygen molecules, it has been assumed that antioxidants such as vitamins C and E could only benefit the body.

A new study published in the Proceedings of the National Academy of Sciences suggests that rather than help protect against oxidative damage from exercise, high doses of antioxidant supplements may actually hinder the body’s natural protection against oxidative damage and block exercise-induced metabolic benefits.

In the study, human subjects were given either placebo or 500 mg vitamin C twice per day and 400 IU vitamin E. They were then trained in both cardio and strength training workouts at the gym for 5 consecutive weekdays, 4 weeks in a row. This trial was performed on both previously trained and untrained individuals.

Metabolic rates were tested by blood sample both before the trial and after 1 and 4 weeks of training. Muscle biopsies were taken both before and after the trial for all participants. Several measures of metabolism and insulin sensitivity were measured including plasma glucose concentrations, plasma insulin concentrations, maximal oxygen uptake (VO₂ max), as well as several molecular markers in muscle that are linked to insulin sensitivity and are known to promote the body’s natural defense against oxidative damage.

The researchers found that exercise improved measures of insulin sensitivity in all individuals except those given antioxidant supplements. Also, molecules that protect against oxidative damage are upregulated in response to training, but not when antioxidants are administered.

Previous studies suggest that the body’s natural defenses against oxidative damage require activation by a small amount of reactive oxygen chemicals in the body. These same chemicals have been shown to mediate insulin sensitivity in muscles, and in this study both were shown to be blocked by high antioxidant administration.

The researchers suggest that small doses of reactive oxygen molecules such as the amounts produced by exercise are necessary to induce the body’s natural defense against oxidative damage, and that this process is essential for mediating exercise-induced insulin sensitivity. If this is true it could mean that some (but not all) of the metabolic benefits of exercise could be limited by taking high doses of vitamin supplements. This may be particularly important to individuals at high risk for type 2 diabetes.

Interestingly, foods that contain high levels of these antioxidants have previously been shown to be protective against type 2 diabetes. Although the reason for this is still unknown, the authors suggest the benefit is unlikely due to the antioxidant content of the foods and may depend on other factors.

Even if we do not understand the reason vegetables and fruits are the best source of nutrition, we can still enjoy all their benefits. If you choose to continue taking vitamin supplements, it is advisable to stick to a basic multivitamin that does not contain megadoses of one particular nutrient.

Do you take vitamin supplements? Why? How much do you take?

Tags: antioxidants, insulin, insulin sensitivity, metabolism, PNAS, Synapse, type 2 diabetes, vitamin C, vitamin E, workout

A widely publicized study out this week in the New England Journal of Medicine shows that there is virtually no difference between low-carb, low-fat, high-carb or high-protein diets when it comes to weight loss. I don’t often like to toot my own horn, but if you read my post on Monday about the Top 10 Food Facts Everyone Should Know (see point #10), then this was not news to you.

For several years now data has been accumulating that the relative composition of different macronutrients (fat, carbs, protein) in your diet has little to no effect on long-term weight loss. What makes this study stand out from the pack is how well it was designed.

The Study

This was the largest, longest run study of this kind ever conducted, including nearly 650 over weight individuals of diverse racial, socioeconomic, geographic and education backgrounds. The participants were highly motivated to lose weight and were given detailed instructions on why their assigned diet was considered an effective weight loss strategy (this was to remove bias caused by the media about popular diets).

For you carbophobes out there, the importance of dietary carbohydrates was addressed directly. The amount of carbohydrates in the different diets varied from 35% (very low) to 65% (very high). All participants, including those on the high-carb diet, were instructed to choose foods that had lower glycemic index. Carbohydrate composition had no significant effect on long-term weight loss.

All subjects received substantial behavioral therapy to help them meet their goals, and detailed measurements of health and weight loss were collected from each individual throughout the study. The participants were told to keep food journals and use online support provided, as well as weekly dietary counseling.

Importantly, all the diets resulted in similar calorie deficiencies to promote weight loss. Not surprisingly, after 6 months all the participants had lost a substantial amount of weight, but after 1 year had gained about half of it back. During the final year the subjects had more difficulty sticking to their assigned diets, particularly those assigned the most extreme regimens (very low-fat or high-protein).

Conclusions

Regardless of diet, all participants experienced similar, modest (5% body weight reduction), but clinically relevant weight loss that is mainly attributed to a reduction in calories.

Interestingly, the measure that best correlated with weight loss success was attendance at the dietary counseling sessions.

Since the study is over can we now assume that many of these participants have gone back to their old eating habits? I would bet yes.

What can we take away from this study?

You can lose weight on any diet, but for most people it is very difficult and not sustained. This is because cutting calories is very tough for most people.

This study also suggests that losing weight with standard diets is very difficult and, in most cases, only moderately helpful. It seems future research should focus on how to increase adherence to a lower calorie diet. Gaming the system by manipulating macronutrient composition doesn’t seem to be working.

Why you should focus on whole foods, not nutrients

Another thing we can take from this study is that if weight loss is your goal, calories are what count. (Some of my friends responded to this finding brilliantly: “DUH.”) The nice thing about a diet based primarily on vegetables is that lowering caloric intake is relatively easy. As long as some effort is made to achieve a balanced diet (enough plant protein and fats), satisfaction after a meal can be attained with far fewer calories.

Vegetables are very bulky, highly nutritious and have very few calories. It’s not easy to gain weight when you eat kale, beans and brown rice for dinner.

Like I explained a few weeks ago, since I have focused on health (rather than weight) and a vegetable-based (rather than macronutrient-based) diet, I have lost weight effortlessly. I am also less stressed about food in general, and have completely lost my old cravings for sugar and fat.

Best of all, I do not feel like I have given up anything whatsoever. In fact I would argue I have gained the freedom to eat what I want, whenever I want it. And the food I eat is much more satisfying and delicious. I guarantee you this tagine tasted better than any Atkins bar, rice cake or BigMac.

My life now is much more delicious.

Are you ready to give up diets and focus on health?

Tags: high-protein, low-carb, low-fat, New England Journal of Medicine

A study published last week in the journal Obesity may make you question whether you really want to rely on the Atkins or South Beach diets to reach your New Year’s Resolution goals.

It is widely believed that low-carbohydrate, high-fat diets support weight loss in most individuals and indeed, there is a good amount of research to back this claim. Despite this, few studies have examined the after effects of a low-carb diet, particularly once normal eating is resumed.

In a new study, scientists had rats consume either a regular high-carb diet or a low-carb, high-fat diet for sixteen days. After this period the diets were switched and rats were maintained on the opposite diet for another sixteen days. Both diets included the same number of calories, so the only difference between the groups was the relative percentage of macronutrients.

As you might expect, while the rats were fed a low-carb, high-fat diet they lost weight compared to rats on a regular diet. Interestingly, however, despite this loss of body weight there was little to no loss of fat, and therefore the rats that lost weight had a relatively higher body fat percentage than the rats fed a normal diet.

The low-carb rats also had lower energy expenditure (exercise and calorie burning) than rats on a normal diet, and the decrease persisted even when the animals were returned to a normal diet. This is consistent with reports of exhaustion in humans undergoing very low-carb diet regimens.

Furthermore, animals that were temporarily put on a low-carb diet regained more weight than animals that were never fed a low-carb diet. This suggests that short term exposure to a low-carb diet increases risk of weight gain compared to no dieting.

Uh oh.

According to this research it is possible that a low-carb diet may actually cause you to gain weight in the long run. How very unfortunate.

But while these results are compelling, do not go stocking up on pasta just yet. First remember that these are rats, not humans. The way scientists change the composition of a rat’s diet is by giving them different pellets of bizarre lab food with various proportions of “nutrients.” This is not the way humans eat (assuming you don’t spend too much time in GNC), nor can it ever reflect a healthy human diet. It would be great if they could put the rats on a diet of seasonal fruits and vegetables, whole grains, legumes and fatty fish, but that is not the way animal research works. This is something to keep in mind whenever you hear about nutrition studies.

Also, nutrition research using rodents rarely distinguishes between the qualities of different macronutrients. For example, did the “high-fat” diet contain mostly saturated fat, trans fat, monounsaturated fats, polyunsaturated fats or all of the above? A similar question can be asked about the quality of carbohydrates, but it is difficult to imagine high-quality carbohydrates coming in pellet form. A huge body of scientific literature suggests that the quality of different macronutrients is far more important to health and weight than relative proportions of refined macronutrients.

Protein is another question mark in this study, which the authors acknowledge. The low-carb diet they used was not high in protein like a typical Atkins style diet. However, their findings were similar to studies that did use higher protein content and their animals were fed sufficient protein to maintain normal body growth, so the effect of protein on their findings is likely to be small. Their goal was to examine the effect of extreme carbohydrate restriction, and this was accomplished.

Regardless of this study’s imperfections, the results shine an interesting light on our current understanding of how relative proportions of dietary macronutrients effect body composition, long-term body weight and metabolism.

Have you experienced weight gain after going off a low-carb diet?

UPDATE: This article is also available at Synapse.

Tags: body fat, low-carb, Obesity

A study published today in the Journal of Neuroscience indicates that certain individuals are more susceptible to images of appetizing food, making them hungrier and raising their risk of overeating.

The study

Scientists at the University of Cambridge in the United Kingdom used functional magnetic resonance imaging (fMRI) to examine the neural network connections of people either more or less sensitive to images of delicious looking desserts. The most sensitive individuals had stronger brain connections between regions known to be involved in impulse and reward circuitry.

Also, the degree of a person’s sensitivity predicted how much he or she wants to eat after seeing appetizing food, and can affect overeating even in the absence of hunger.

This study is the first to examine the neural networks involved in food suggestibility in humans, but it supports similar findings reported in rodents.

The implication is that some people may be much more strongly influenced by food advertising than others, a phenomenon that can trigger overeating and ultimately weight gain.

What does this mean for you?

My guess is that you know whether or not you are someone who is deeply affected by images of food. This might suggest it is in your best interest to actively avoid watching commercials and flipping through glossy food magazines (and blogs) with images of decadent foods.

If you really enjoy food publications (I hope you do!) you could try switching to something like Cook’s Illustrated, where the images are technical rather than appetizing. The best alternative, however, may be to only tune in to those media sources that make healthy food look delicious, like this blog!

I definitely won’t be offering up pictures of chocolate cake and cookies in the near future.

What do you think, are you deeply affected by images of food and does it make it difficult for you to control what you eat?

Tags: Journal of Neuroscience, overeating

To be honest, I don’t really believe in the New Year’s Resolution. By nature I am a person of action and do not need an excuse to make my own life better.

If there is something important in my daily routine that I feel needs improvement I don’t wait for January to make the change. Instead I live by the Nike slogan and Just Do It.

Thus the first question I pose to readers today is:

Does a new digit at the end of the calendar really make it easier to go to the gym or eat a salad?

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Next there is the issue of sticking to your Resolution. From what I understand, most people abandon their New Year’s ambitions after a couple months (or even weeks) of half-hearted effort.

To me this proves that resolving to do something is relatively meaningless. In my opinion, if there is any point to this year-end exercise at all, things must actually get done.

Maybe we should change the name to New Year’s Solution?

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But perhaps I am too harsh.

Rather than hoping for change, for many people the New Year may simply be a time for reflection and evaluation:

What has and hasn’t worked in 2008? Should I approach anything differently in 2009?

This kind of personal reflection I applaud, but what still troubles me is that so many people make the same Resolutions year after year without ever achieving their goals.

This year I will lose weight! This year I will get in shape! This year I will use my gym membership!

If you don’t believe me take a stroll through your local Borders or Barnes & Noble bookstore and check out the number of diet books on display at the front. Notice their bright pinks and yellows designed to get your attention.

Never is the promotion of weight loss books as shameless as it is in January.

We are all supposed to try our failed resolutions again this year, keeping the hope alive that one of those neon programs will become our salvation and finally we will achieve our lifelong dream of being thin and happy.

*yawn*

I am not interested in this phony brand of Resolution.

Over and over diets have been shown not to work and even promote weight gain, so they are not your answer.

Health problems and body fat do not appear in a single splurge, but rather accumulate bit at a time as a result of poor lifestyle decisions. So it is not logical to believe that a quick, short-term weight loss will correct them.

This year (as in every year) I recommend moderation as the best solution for health. And I propose that the most effective way to build good habits and reduce bad ones is to make small, gradual changes to your daily routine.

Moderate changes that you can easily manage are the ones that can be maintained and built upon.

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If you do intend to make changes to your habits this year, I wish you the best of luck. I designed this blog to provide tips, advice and information to help cultivate a practical, healthy lifestyle.

My approach begins with establishing the mentality that diets don’t work and health is achieved through habits, not single actions. With a handful of tools and simple tricks, even the busiest among us can streamline health to be an automatic part of our lives.

To get the most out of Thought for Food, subscribe via email or RSS feed.

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On a final note, the road to health begins with inspiration.

This year I would love to learn your personal New Year’s Resolution success stories. Were you ever able to quit smoking? Maintain your workout routine? Lose weight? Adopt a new hobby?

I invite you to share with us your New Year’s Solution and tell us what obstacles you overcame and why you think you were able to achieve your goal.

Your success could inspire the rest of us to find New Year’s Solutions of our own!

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Discuss Thought for Food:

1. Does the New Year help you make improvements in your life?
2. Do you think there is a difference between a Resolution and a Solution?
3. Is moderation a reasonable alternative to dieting?
4. Do you have a New Year’s Solution to share?

Tags: moderation, New Year's