Are All Calories Created Equal?

Written by Dr. Steve Chaney on . Posted in current health articles, Food and Health, Nutritiion

Are Food Choices More Important Than Calories?Author: Dr. Stephen Chaney

 

Most adult Americans gain a pound or two each year. That may not sound like much on a yearly basis, but over a lifetime it is huge – if you’ll pardon the pun.

are all calories created equalBecause the health consequences of weight gain are so devastating, everyone has their favorite dietary advice for keeping those extra pounds away. For some it is diet plans – low fat, low carb, paleo, Mediterranean – you name it. For others it is counting calories or avoiding sugars of all kinds. The list goes on. Are all calories created equal?

But what if all of these approaches were wrong? What if we could keep our weight under control solely based on the foods we eat? A recent study seemed to suggest that we just might.

How Was The Study Designed?

A group of scientists from Tufts University and Harvard decided to look at how the food choices we make on a daily basis influence our weight gain or loss over time (Smith et al, AJCN 101: 1216-1224, 2015). However, they designed their study in a very unique way, and it is important that I explain the study design so that you can understand the strengths and limitations of the study.

Most studies of this kind look at what foods people are eating and compare that to how much they weigh. These scientists looked at changes that people made in their diets and correlated that with how much weight they gained or lost over time.

When you think of it, that’s the information most of us really want to know. We are less interested in why the foods we used to eat got us into trouble in the first place than we are in how the changes we make in our diet might influence future weight loss or gain.

This study combined the data from three very large, long term studies – the Nurses’ Health Study, the Nurses’ Health Study II, and the Health Professionals Follow-Up Study. Altogether that is a group of 120,784 men and women who were followed for 16-24 years. All three of these studies measured weight and evaluated dietary habits using food-frequency questionnaires every 4 years.

The scientists conducting the study measured changes in food choices and changes in weight for each individual in 4-year increment over the total time duration of the studies. In analyzing the data, they looked at choices of protein foods, total carbohydrate, and the glycemic load (GL) of the carbohydrates.

Glycemic load is the glycemic index (effect on blood sugar) of the carbohydrates in a particular food times the total amount of carbohydrate in that food. You can think of glycemic load as a measure of carbohydrate quality. For example, white bread, pastries, muffins, pancakes, white rice, chocolates, candy bars, cookies, brownies, cakes, pies, and pretzels would all be examples of foods with a high glycemic load. Fruits, whole grain foods and starchy vegetables would be examples of foods with a moderate glycemic load. Vegetables and beans would be examples of foods that generally have a low glycemic load.

The authors of the study did not measure calories or fat intake for this study, but those factors are indirectly included in food choices – more about that later.

Are All Calories Created Equal?

Now let’s get to the good stuff – the results of this study. When the authors analyzed the data they found that:

  • Most of the subjects did not exchange one protein food for another over the course of the study. They exchanged protein foods for carbohydrate-rich foods and vice versa.

This was a surprise. Since many experts have been recommending that people substitute chicken and fish for red meat, they had expected to see that kind of dietary shift when they analyzed the data. Apparently, people have not been listening to the experts!

  • high carbohydratesWhen the subjects replaced a serving of carbohydrate-rich foods with a serving of red meats, processed meats, chicken with skin or most cheeses they gained between 0.5 to 2.3 pounds per year. Within this category the greatest weight gain was seen when hamburgers were substituted for carbohydrates, and the least weight gain was seen when cheese was substituted for carbohydrates.
  • When the subjects replaced a serving of carbohydrate-rich foods with a serving of milk, peanuts or eggs there was no net change in weight. These appear to be substitutions that are good for weight maintenance.
  • When the subjects replaced a serving of carbohydrate-rich foods with a serving of yoghurt, peanut butter, beans, walnuts, other nuts, chicken without skin, low-fat cheese or seafood they lost between 0.5 and 1.5 pounds/year. Within this category the greatest weight loss was seen when plain yoghurt was substituted for carbohydrates, and the least weight loss was seen when low-fat cheese was substituted for carbohydrates.
  • When they focused on carbohydrate-rich foods, replacing one serving of high glycemic load foods with low glycemic load foods was associated with one pound of weight loss per year. Simply put, if you switch from cookies, pastries and candies to fruits and vegetables, you are likely to lose weight. No surprise here.

The study really got interesting when they looked at the effect of adding different proteins in the context of the carbohydrate-rich foods that the subjects were eating. For example,

  • When the subjects added a serving of red meat to a diet containing carbohydrate foods with a high glycemic load, they gained an average of 2.5 pounds per year. When they added that same serving of red meat to a diet containing carbohydrate foods with a low glycemic index, they gained only around 1.5 pounds per year.

Simply put, that means eating a hamburger on a white flour bun with fries is going to pack on more pounds than a hamburger patty with brown rice and a green salad.

  • The effect of glycemic load was particularly interesting when you looked at the protein foods that were good for weight maintenance overall. For example, adding a serving of eggs to a high glycemic load diet resulted in a 0.6 pound/year weight gain, while adding that same serving of eggs to a low glycemic load diet resulted in a 1.75 pound/year weight loss. The results were similar for cheeses.
  • Finally, glycemic load also influenced the effectiveness of protein foods associated with weight loss. For example, addition of a serving of beans to a high glycemic load diet resulted in 0.5 pound/year weight gain loss, but adding a serving of beans to a low glycemic load diet resulted in a 1.5 pound/year weight loss.

New Insights From This Study

good proteinThis study broke new ground in several areas. For example,

  • We have heard over and over that substituting beans, chicken and fish for red meats is healthier. This is the first study I have heard of that says those same substitutions can prevent or reverse weight gain.
  • Many people advocate a high protein diet for weight control or weight loss, but many of them will tell you the type of protein doesn’t matter. This study suggests that the type of protein foods we eat are important in determining whether we lose or gain weight.
  • Everyone knows that switching from white grains, pastries and candy to whole grains, fruits and vegetables will help you lose weight, but this is the first study I’m aware of that suggests those same changes will influence whether the protein foods we eat lead to weight gain or weight loss.
  • Many people focus on fats and calories when trying to avoid weight gain. While this study is not really fat and calorie neutral (see below), it does suggest that if we focus on eating healthy foods we don’t need to be counting every fat gram and every calorie.
  • Finally, this study suggests that if we forget all of those crazy diets and focus on eating healthy foods, our weight will take care of itself. Not exactly a novel concept, but one worth repeating.

Limitations of the Study

The head author of this study stated in an interview “The idea that the human body is just a bucket for calories is too simplistic. It’s not just a matter of thinking about calories or fat. What’s the quality of the foods we are eating? And how do we define quality.” This has been picked up by the media with statements like “not all calories are created equal”.

That is a bit of a hyperbole, because this study is not really fat and calorie neutral. The protein foods (red and processed meats) that pack on the most calories are higher in fat and calories per serving than those protein foods (skinless chicken, fish and beans) that cause the least weight gain. Similarly, the carbohydrate foods with the highest glycemic load (pastries, cakes and candy) are higher in fat and calories per serving than those carbohydrate foods with the lowest glycemic load (fruits and vegetables).

The real message is not that fat content and calories don’t count. Nor is it that calories in some foods count more than the same calories in other foods. The take home lesson from this study should be that we don’t have to focus on fat and calories. If we focus on healthy foods, the fat and calories tend to take care of themselves.

But, even that message is a bit too simplistic. Choosing healthy foods is not all that there is for weight control. We also need consider:

  • Portion sizes. Half a chicken could easily add more calories than a small hamburger.
  • How the food is cooked. Fish cooked in a cream sauce may not be any better for weight control than a slab of red meat.
  • Exercise. We need to maintain muscle mass to keep metabolic rate high.

 

The Bottom Line

  • A recent study has broken new ground and provided some new insights into how to prevent those extra pounds from sneaking up on us over time. This study evaluated how some simple changes we could make in the foods we eat can influence whether we gain or lose weight.
  • One part of the study looked at the effects of replacing a serving of carbohydrate rich foods with a serving of protein rich foods. If that protein rich food were a hamburger, we could expect to gain about 2.3 pounds/year. If that protein rich food were seafood, we could expect to lose about 1.5 pounds/year. Other protein foods fall in between those extremes. The specifics are covered above.

This a new insight. Many people advocate a high protein diet for weight control or weight loss, but many of them will tell you the type of protein doesn’t matter. So, are all calories created equal?  This study suggests that the type of protein foods we eat are important in determining whether we lose or gain weight.

  • Another part of the study looked at the effect of different carbohydrate foods based on their glycemic load (the effect they have on blood sugar). Simply replacing 1 serving of high glycemic load foods (refined grain foods, cookies, cakes, candy) with low glycemic load foods (whole grains, fruits and vegetables) was associated with a one pound/year weight loss. This should surprise no one.
  • Finally, one part of the study looked at the influence of glycemic load on the effect that various proteins have on weight gain or loss. For example, adding a serving of eggs to a high glycemic load diet resulted in a 0.6 pound/year weight gain, while adding that same serving of eggs to a low glycemic load diet resulted in a 1.75 pound/year weight loss. Other examples are given above.

This is also a new insight. Everyone knows that switching from white grains, pastries and candy to whole grains, fruits and vegetables will help you lose weight, but this is the first study I’m aware of that suggests those same changes will influence whether the protein foods we eat lead to weight gain or weight loss.

  • Some in the media have interpreted this study as saying that fat and calories don’t count. However, this study was not really fat and calorie neutral. The protein and carbohydrate rich foods that packed on the most calories were also the foods highest in fat and calories. The real take home message from this study is that we may not need to focus so much on fat and calories. When we focus on eating healthy foods the fat and calories tend to take care of themselves.
  • Even that message is a bit too simplistic. It is not enough to just focus on healthy foods. We need to consider things like portion size, how the food is prepared, and our exercise habits among other things.

 

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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A Low Carb Diet and Weight Loss

Posted January 15, 2019 by Dr. Steve Chaney

Do Low-Carb Diets Help Maintain Weight Loss?

Author: Dr. Stephen Chaney

 

low carb dietTraditional diets have been based on counting calories, but are all calories equal? Low-carb enthusiasts have long claimed that diets high in sugar and refined carbs cause obesity. Their hypothesis is based on the fact that high blood sugar levels cause a spike in insulin levels, and insulin promotes fat storage.

The problem is that there has been scant evidence to support that hypothesis. In fact, a recent meta-analysis of 32 published clinical studies (KD Hall and J Guo, Gastroenterology, 152: 1718-1727, 2017 ) concluded that low-fat diets resulted in a higher metabolic rate and greater fat loss than isocaloric low-carbohydrate diets.

However, low-carb enthusiasts persisted. They argued that the studies included in the meta-analysis were too short to adequately measure the metabolic effects of a low-carb diet. Recently, a study has been published in the British Medical Journal (CB Ebbeling et al, BMJ 2018, 363:k4583 ) that appears to vindicate their position.

Are low carb diets best for long term weight loss?

Low-carb enthusiasts claim the study conclusively shows that low-carb diets are best for losing weight and for keeping it off once you have lost it. They are saying that it is time to shift away from counting calories and from promoting low-fat diets and focus on low-carb diets instead if we wish to solve the obesity epidemic. In this article I will focus on three issues:

  • How good was the study?
  • What were its limitations?
  • Are the claims justified?

 

How Was The Study Designed?

low carb diet studyThe investigators started with 234 overweight adults (30% male, 78% white, average age 40, BMI 32) recruited from the campus of Framingham State University in Massachusetts. All participants were put on a diet that restricted calories to 60% of estimated needs for 10 weeks. The diet consisted of 45% of calories from carbohydrate, 30% from fat, and 25% from protein. [So much for the claim that the study showed low-carb diets were more effective for weight loss. The diet used for the weight loss portion of the diet was not low-carb.]

During the initial phase of the study 161 of the participants achieved 10% weight loss. These participants were randomly divided into 3 groups for the weight maintenance phase of the study.

  • The diet composition of the high-carb group was 60% carbohydrate, 20% fat, and 20% protein.
  • The diet composition of the moderate-carb group was 40% carbohydrate, 40% fat, and 20% protein.
  • The diet composition of the low-carb group was 20% carbohydrate, 60% fat, and 20% protein.

Other important characteristics of the study were:

  • The weight maintenance portion of the study lasted 5 months – much longer than any previous study.
  • All meals were designed by dietitians and prepared by a commercial food service. The meals were either served in a cafeteria or packaged to be taken home by the participants.
  • The caloric content of the meals was individually adjusted on a weekly basis so that weight was kept within a ± 4-pound range during the 5-month maintenance phase.
  • Sugar, saturated fat, and sodium were limited and kept relatively constant among the 3 diets.

120 participants made it through the 5-month maintenance phase.

 

Do Low-Carb Diets Help Maintain Weight Loss?

low carb diet maintain weight lossThe results were striking:

  • The low-carb group burned an additional 278 calories/day compared to the high-carb group and 131 calories/day more than the moderate-carbohydrate group.
  • These differences were even higher for those individuals with higher insulin secretion at the beginning of the maintenance phase of the study.
  • These differences lead the authors to hypothesize that low-carb diets might be more effective for weight maintenance than other diets.

 

What Are The Pros And Cons Of This Study?

low carb diet pros and consThis was a very well-done study. In fact, it is the most ambitious and well-controlled study of its kind. However, like any other clinical study, it has its limitations. It also needs to be repeated.

The pros of the study are obvious. It was a long study and the dietary intake of the participants was tightly controlled.

As for cons, here are the three limitations of the study listed by the authors:

#1: Potential Measurement Error: This section of the paper was a highly technical consideration of the method used to measure energy expenditure. Suffice it to say that the method they used to measure calories burned per day may overestimate calories burned in the low-carb group. That, of course, would invalidate the major findings of the study. It is unlikely, but it is why the study needs to be repeated using a different measure of energy expenditure.

#2: Compliance: Although the participants were provided with all their meals, there was no way of being sure they ate them. There was also no way of knowing whether they may have eaten other foods in addition to the food they were provided. Again, this is unlikely, but cannot be eliminated from consideration.

#3: Generalizability: This is simply an acknowledgement that the greatest strength of this study is also its greatest weakness. The authors acknowledged that their study was conducted in such a tightly controlled manner it is difficult to translate their findings to the real world. For example:

  • Sugar and saturated fat were restricted and were at very similar levels in all 3 diets. In the real world, people consuming a high-carb diet are likely to consume more sugar than people in the other diet groups. Similarly, people consuming the low-carb diet are likely to consume more saturated fat than people in the other diet groups.
  • Weight was kept constant in the weight maintenance phase by constantly adjusting caloric intake. Unfortunately, this seldom happens in the real world. Most people gain weight once they go off their diet – and this is just as true with low-carb diets as with other diets.
  • The participants had access to dietitian-designed prepared meals 3 times a day for 5 months. This almost never happens in the real world. The authors said “…these results [their data] must be reconciled with the long-term weight loss trials relying on nutrition education and behavioral counseling that find only a small advantage for low carbohydrate compared with low fat diets according to several recent meta-analyses.” [I would add that in the real world, people do not even have access to nutritional education and behavioral modification.]

 

low carb diet and youWhat Does This Study Mean For You?

  • This study shows that under very tightly controlled conditions (dietitian-prepared meals, sugar and saturated fat limited to healthy levels, calories continually adjusted so that weight remains constant) a low-carb diet burns more calories per day than a moderate-carb or high-carb diet. These findings show that it is theoretically possible to increase your metabolic weight and successfully maintain a healthy weight on a low-carb diet. These are the headlines you probably saw. However, a careful reading of the study provides a much more nuanced viewpoint. For example, the fact that the study conditions were so tightly controlled makes it difficult to translate these findings to the real world.
  • In fact, the authors of the study acknowledged that multiple clinical studies show this almost never happens in the real world. These studies show that most people regain the weight they have lost on low-carb diets. More importantly, the rate of weight regain is virtually identical on low-carb and low-fat diets. Consequently, the authors of the current study concluded “…translation [of their results to the real world] requires exploration in future mechanistic oriented research.” Simply put, the authors are saying that more research is needed to provide a mechanistic explanation for this discrepancy before one can make recommendations that are relevant to weight loss and weight maintenance in the real world.
  • The authors also discussed the results of their study in light of a recent, well-designed 12-month study (CD Gardener et al, JAMA, 319: 667-669, 2018 ) that showed no difference in weight change between a healthy low-fat versus a healthy low-carbohydrate diet. That study also reported that the results were unaffected by insulin secretion at baseline. The authors of the current study noted that “…[in the previous study] participants were instructed to minimize or eliminate refined grains and added sugars and maximize intake of vegetables. Probably for this reason, the reported glycemic load [effect of the diet on blood sugar levels] of the low-fat diet was very low…and similar to [the low-carb diet].” In short, the authors of the current study were acknowledging that diets which focus on healthy, plant-based carbohydrates and eliminate sugar, refined grains, and processed foods may be as effective as low-carb diets for helping maintain a healthy weight.
  • This would also be consistent with previous studies showing that primarily plant-based, low-carb diets are more effective at maintaining a healthy weight and better health outcomes long-term than the typical American version of the low-fat diet, which is high in sugar and refined grains. In contrast, meat-based, low-carb diets are no more effective than the American version of the low-fat diet at preventing weight gain and poor health outcomes. I have covered these studies in detail in my book “Slaying The Food Myths.”

Consequently, the lead author of the most recent study has said: “The findings [of this study] do not impugn whole fruits, beans and other unprocessed carbohydrates. Rather, the study suggests that reducing foods with added sugar, flour, and other refined carbohydrates could help people maintain weight loss….” This is something we all can agree on, but strangely this is not reflected in the headlines you may have seen in the media.

The Bottom Line

 

  • A recent study compared the calories burned per day on a low-carb, moderate-carb, and high-carb diet. The study concluded that the low-carb diet burned significantly more calories per day than the other two diets and might be suitable for long-term weight control. If confirmed by subsequent studies, this would be the first real evidence that low-carb diets are superior for maintaining a healthy weight.
  • However, the study has some major limitations. For example, it used a methodology that may overestimate the benefits of a low-carb diet, and it was performed under tightly controlled conditions that can never be duplicated in the real world. As acknowledged by the authors, this study is also contradicted by multiple previous studies. Further studies will be required to confirm the results of this study and show how it can be applied in the real world.
  • In addition, the kind of carbohydrate in the diet is every bit as important as the amount of carbohydrate. The authors acknowledge that the differences seen in their study apply mainly to carbohydrates from sugar, refined grains, and processed foods. They advocate diets with low glycemic load (small effects on blood sugar and insulin levels) and acknowledge this can also be achieved by incorporating low-glycemic load, plant-based carbohydrates into your diet. This is something we all can agree on, but strangely this is not reflected in the headlines you may have seen in the media.
  • Finally, clinical studies report averages, but none of us are average. When you examine the data from the current study, it is evident that some participants burned more calories per hour on the high-carb diet than other participants did on the low carb diet. That reinforces the observation that some people lose weight more effectively on low-carb diets while others lose weight more effectively on low-fat diets. If you are someone who does better on a low-carb diet, the best available evidence suggests you will have better long-term health outcomes on a primarily plant-based, low-carb diet such as the low-carb version of the Mediterranean diet.

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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