Exercise and Weight Loss

Written by Dr. Steve Chaney on . Posted in current health articles, Exercise, Healthy Lifestyle, Lose Weight

Author: Dr. Stephen Chaney

exercise and weight lossAre you confused yet?  Just as you were starting to wrap your mind around the current consensus recommendations that we engage in 30 minutes of moderate intensity exercise 5 days/week, news stories are starting to appear saying that might not be enough exercise if you want to lose weight!

So how much exercise DO you need, and why is there so much confusion with exercise and weight loss?

Let me start by reviewing a couple of studies that appeared a few years ago on weight loss in middle aged, overweight women.

 

Exercise and Fat Loss

The first study looked at the effect of exercise intensity on abdominal fat loss over a 16-week period(Irving et al, Medicine & Science In Sports & Exercise,40: 1863-1872, 2008).

The women in this study were divided into three groups:the control group that just continued their normal exercise pattern (little or none), a group that engaged in supervised moderate intensity exercise 5 days per week, and a group that engaged in supervised, high intensity exercise 3 days per week and moderate intensity exercise the other two days.

The diet was identical for all three groups and the calories expended by exercise were also identical (the high intensity exercise was performed for shorter periods of time so that the calories expended were the same).

The results were striking. Weight loss was similar in the two exercise groups (calories do count). However, the women in the high intensity exercise group lost a significant amount of abdominal fat while the other two groups did not! As you may know, abdominal fat appears to be much more damaging metabolically than fat stores in other parts of our bodies.

 

Exercise and Weight Loss

woman runningThe second study looked at the effect of exercise duration on weight loss over a 24-month period (Jackcicet al, Archives of Internal Medicine, 168: 1550-1559,2008).

In this case the diet and the intensity of the exercise(moderate intensity) were the same. The difference was in the duration of the exercise. In this case the calories expended by exercise was not kept the same. The group that exercised for longer burned significantly more calories than those who exercise for a shorter time.

Again the results were striking. Only those study participants who exercised for at least 275 minutes/week (an average of almost 60 minutes a day for 5 days) were able to lose 10% or more of their weight and keep the weight off over a 24-month period.

 

How Much Exercise is Enough?

So what does all of this mean to you?

how much exercise is enoughWhen most Americans decide to shed a few pounds, one of the first things they think of is getting more exercise. After all, it’s much easier to walk around the block during lunch hour than to actually change what you are eating.

The question then becomes how much exercise is enough? Is the recommended 30 minutes a day of moderate intensity exercise 5 days per week enough?

If you actually work through the math, it is pretty easy to guess that it might not be enough. For example, a recent study looked at how much moderate intensity exercise would be required for a 155-pound woman to burn off the calories in same popular fast foods. For example, to burn off the calories:

  • In a MacDonald’s Big Mac, she would need to cycle at a moderate pace for 1 hour.
  • In an Arby’s Reuben, she would need to walk at a moderate pace for 3 hours.
  • In a Super Sonic Double Cheeseburger with Mayo, she would need to do low impact aerobics for 3 hours.

Of course, if she had fries and a soda with any of those meals she would need to do even more exercise.

weight loss and dietThese estimates are not just hypothetical. The studies described above clearly show that if you are relying on exercise alone to shed your excess pounds and/or excess fat, you are going to need higher intensity exercise and/or longer duration moderate intensity exercise than the current consensus recommendations suggest.

In other words, the current recommendations of 30 minutes of moderate intensity exercise 5 days per week probably won’t make much of a dent in your weight unless the exercise is coupled with a very good weight loss program.

But, if you have ever relied on exercise alone for weight loss, you have probably guessed that already!

Of course, the consensus recommendations are still valid for what they were designed to accomplish. 30 minutes a day of moderate intensity exercise 5 days per week is sufficient to improve fitness and reduce cardiovascular risk factors.  And fitness reduces your risk of disease even if you are still overweight.

Furthermore, since many Americans probably don’t get even 30 minutes of exercise in a week, 30 minutes 5 days per week is a great starting goal.

 

The Bottom Line 

Recent studies show that the current recommendations of 30 minutes of moderate intensity exercise 5 days per week probably won’t make much of a dent in your weight unless the exercise is coupled with a very good weight loss program.

Don’t freak out about all of the conflicting exercise recommendations. Here’s what I suggest:

1) Consult with your physician before you start any exercise program.

2) Get active. Start slowly and start by choosing activities that are fun and accessible to you.

3) Set your goal of 30 minutes of moderate intensity exercise 5 days per week. If you want to lose weight, couple that with a well-designed weight loss program.

4) If your combination of exercise and diet isn’t putting a dent in your weight and weight loss is important to you, pick up the pace or increase the duration of exercise.

 

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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Comments (2)

  • Helen T. Govedarica

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    Thank you for your wonderful info laden emails. They help me feel more knowledgeable when talking to my downline.

    Please note I have a new email address and am just making sure that you have changed your records.

    Thank You.

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    • Dr. Steve Chaney

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      Your records have been updated

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Latest Article

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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