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