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Exercise and Weight

November 30, 2009 Written by JP       [Font too small?]

I hear a lot of advice about diet and exercise in my daily life. Many of the statements made by so-called experts and laypeople alike are quite definitive in nature. “Eating fatty foods and sugar will make you fat.” “The key to staying slim is moderation.” “It doesn’t matter what you eat, just eat sensibly.” “You need to exercise if you really want to lose weight. Diet alone won’t cut it.” But nutrition, much like life, is shaded with many gray areas. There are fine distinctions that apply to almost every diet “rule”. One aspect of weight loss which received a lot of attention this year has to do with the role that exercise plays in weight management.

A recent study involving 4,456 female adolescents supports an emerging point of view in the field of obesity treatment: exercise tends to be more effective in preventing weight gain rather than promoting weight loss. This comes on the heals of a wildly popular Time Magazine article from August 2009 entitled, “Why Exercise Won’t Make You Thin”. My goal today will be to add some additional science to this current debate. (1,2)

One interesting experiment that I found focuses on the timing of exercise. A group of scientists from the University of Michigan, Ann Arbor determined that walking on a treadmill 1 hour prior to a meal was significantly more effective at lowering blood sugar levels than exercising 1 hour post meal. Pre-meal exercise lead to a 20% reduction in blood glucose levels over a 16 hour period. They also noted a 49% increase in the “insulin-glucagon ratio during meals”. These changes are likely a consequence of “reduced carbohydrate availability during exercise”. Post-meal exercise did not result in any meaningful changes in blood sugar concentrations. Optimal/stable blood sugar assists the body in maintaining a healthy appetite and weight. (3)

The relationship between exercise and meal-mediated blood sugar changes may be different for those with diabetes and metabolic syndrome. A study conducted on 12 type 2 diabetics recently found that 20 minutes of walking after meals was more effective at lowering blood sugar than pre-meal walks or no walking at all. (4)

One of the biggest controversies in the exercise-weight debate revolves around the issue of physical activity and appetite regulation. The $64,000,000,000 question is whether exercise increases appetite. Several new experiments may hold the key to clarifying this issue:

  • A February 2009 study in the journal Appetite determined that exercising 2 hours after a meal could extend “the appetite suppressing effect of food intake”. They also noted an increase in a satiety (“fullness”) hormone known as PYY in subjects who engaged in post-meal exercise. However, there were also benefits found in those who exercised 1 hour prior to a meal. Those individuals demonstrated “decreased appetite and increased plasma ghrelin concentrations”. Ghrelin is yet another hormone that is typically lacking in overweight men and women. (5)
  • A trial involving 29 boys and girls (aged 9-14) discovered that “short duration” (15 minutes) exercise decreased appetite when practiced 2 hours post-meal. However, “long duration” (45 minutes) exercise increased hunger. However, these relative changes in appetite did not result in a statistically different caloric intake. The Canadian researchers who helmed the study commented that “SD (short duration) exercise programs in schools may be an effective strategy for maintaining healthier body weights in children”. (6)
  • A trial presented in the October issue of the American Journal of Clinical Nutrition examined the effects of a 12 week “supervised exercise” program in a group of 58 obese and overweight men and women. The results of this experiment were perhaps the most fascinating yet: a generalized, daily exercise program appears to increase overall hunger but it also helps the body to feel more satisfied with the food we eat. In essence, this would be a “wash” with respect to weight loss. (7)
AT = Brown Adipose (Fat) Tissue     WAT = White Adipose (Fat) Tissue
Source: Diabetes July 2009 vol. 58 no. 7 1482-1484 (link)

Weather conditions can also effect how physical activity impacts the hunger response in the body and brain. A 2009 Australian trial explains that exercising in a warmer environment (36 degrees C) is associated with lower energy intake (fewer calories) as compared to physical activity conducted in “neutral environmental temperature” (25 degrees C). Working out in even colder conditions has previously been connected to increased appetite and higher energy consumption. This effect is significant enough for some researchers to suggest that environmental/weather conditions should be factors in formulating exercise-based weight loss programs. But we must also consider that energy expenditure (calories burned) also tends to be greater in a cold environment. (8,9,10)

In addition to any effect that exercise may or may not have on hunger and weight, it’s important to remember that physical activity positively impacts post-meal health in other ways. Most studies indicate that exercising around meals can lower potentially harmful lipids (triglycerides) and inflammation (IL-6 and C-reactive protein) while increasing healthy (“HDL”) cholesterol concentrations. In fact, as little as 30 minutes of “brisk walking” per day (at any time of the day) may be enough to offset some of the damage caused by a less than perfect diet. All of these findings argue in favor of pre or post meal exercise, especially if you’re overweight or otherwise at risk for blood sugar disorders and cardiovascular disease. (11,12,13,14)

I want to end today’s column with a bit of good old fashioned common sense. Let’s take the worst case scenario, such as that presented in the Time Magazine article. You exercise on a regular basis but find that you don’t lose weight because said exercise increases your appetite. I have a remedy for this but it’s a tough pill to swallow: 1) Stop using food as a reward for exercise. Just because you go walking, doesn’t mean that you should allow yourself extra calories on that day. 2) Realize that exercise *may* stimulate your appetite. If that’s the case, try some of the strategies I’ve outlined here today. If that still doesn’t work, simply be aware of your heightened hunger and choose your foods extra carefully, i.e. avoid high calorie, unhealthy treats and stick with nourishing whole foods. 3) Make sure that you stay active on the days that you exercise. Don’t use exercise as an excuse to be less active than on other days. The key is to add movement (exercise) to your normal routine in order to burn more calories. Exercise can, indeed, help to manage weight provided that you don’t sabotage your efforts by eating more or becoming less active on the days you go for a walk, play a few rounds of golf or spend time at the gym.

Note: Please check out the “Comments & Updates” section of this blog – at the bottom of the page. You can find the latest research about this topic there!

Be well!

JP

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16 Comments & Updates to “Exercise and Weight”

  1. anne h Says:

    Just this weekend I bought a treadmill -
    I know it will soon be too cold to get a meaningful walk in -even here in Texas.
    I’ve already been burning it up at home!
    After a year of walking I can now go at a super slow trot.
    That, plus all the 6000+ steps at work!!

  2. JP Says:

    Good for you, Anne! :)

    I’m taking your lead and starting back up with my own “treadmilling”! Is there such a word? :)

    Thanks for the inspiration!

    Be well!

    JP

  3. Nina K. Says:

    Hello :-) ,

    we just start our winter sports programm ;-) , that means that we are going to the gym. i hate that! i hate the air and doing sports indoors is not so relaxing than walking outside or playing tennis near the forest (fresh air).

    i alternate weight lifting training and endurance training, sometimes i have the impression that i have overtrained and to much cortisol is released, at this point im not hungry because im not relaxed.

    if i have done the right workload but want to cut extra calories i drink a lot: peppermint tea and green tea or a delicate fruit tea supresses feeling hungry very very well.

    despite the fact that doing sports is exhausting ;-) i can highly recommend it ;-) :-)

    Nina K.

  4. Linda Says:

    Hallo, I enjoy all the useful information in your blog. I practise calorie restriction with optimal nutrition (CRON) and do a 20-minute exercise stint most days that lifts my mood and controls hunger. I’ve begun doing this pre-meal lately, which works very well. I wondered about the wisdom of this, but then considered that hunter-gatherers and animals in the wild expend most energy while running on empty, i.e. in order to find or capture their food, and then rest after consuming it.

  5. Troy Lovick Says:

    In our (pediatric & adult)weight management programs we have taken a lesson from the natural activity patterns of normal weight children. Multiple brief periods of moderately vigorous (zone 3) to very vigorous (Zone 4) physical exertion with periods of compete rest in between. So imagine five or six 5 to 7 min bursts of fun engaging activity per day vs. xx min on the treadmill. Thus we advocate increasing activity by accumulation rather than longer blocks of time.
    This pattern is fun for kids and can overcomes the can’t exercise because (fill in the blank) resistance of adults.

  6. JP Says:

    An excellent strategy, Nina! :)

    Be well!

    JP

  7. JP Says:

    Linda,

    I think your observation makes a lot of sense. It’s also cool when science supports our intuition. :)

    Be well!

    JP

  8. JP Says:

    Thank you for sharing that, Troy! It’s invaluable to receive “reports from the field” such as that. :)

    I’ve read several studies that substantiate that type of strategy. It not only makes sense but appears to be more practical for many people. Sounds like a winning combination. :)

    Be well!

    JP

  9. Anonymous Says:

    “Stop using food as a reward for exercise. Just because you go walking, doesn’t mean that you should allow yourself extra calories on that day.”

    I am very guilty of this. My wife and I live down the street from a Dairy Queen. We have ourselves convinced that it is not that bad because we walked there and back. I am sure that would have to be done many more times to work off the ice cream we just consumed. I need to get healthier this coming year. I am out of shape and over weight. Thanks for the encouragement.

  10. JP Says:

    You’re very welcome. :)

    A new year is a great occasion to make healthful changes. I wish you and your all the best with that goal in mind!

    Be well!

    JP

  11. Belen Tanghal Says:

    I have been serving mostly fish and vegetables to my family for 3 years now and I move around more by doing household chores and by walking more. The holidays made me lazy and made me eat more than the usual. It’s time to walk on the healthy road again. Thanks for this article…it was like a wake-up call.

  12. JP Says:

    Thank you, Belen! :)

    I’m very happy to hear that it was a wake-up call. Even though the holidays can be difficult, they also provide us with a fresh start. In your case, they’ll serve as an incentive to walk more! That’s a good thing!

    re: fish and veggies

    Excellent! That’s a wonderful foundation for good health!

    Be well!

    JP

  13. Pradip Gharpure Says:

    Exercise is the assured way to loose weight and get shape. But it needs to be done consistantly and with variations so that you should not feel fatigue and give it up.

  14. JP Says:

    Updated 06/15/16:

    http://www.ncbi.nlm.nih.gov/pubmed/27298806

    J Exerc Nutrition Biochem. 2016 Mar 31;20(1):1-8.

    The combined effect of green tea and acute interval sprinting exercise on fat oxidation of trained and untrained males.

    PURPOSE: This study investigated the combined effect of green tea and acute interval sprinting exercise on fat oxidation of trained and untrained males.

    METHODS: Fourteen trained and 14 untrained males ingested one capsule containing either green tea or cellulose with breakfast, lunch, and dinner, 24 hours before two exercise sessions. A fourth capsule was consumed 90 minutes before exercise after overnight NPO (nil per os). Participants performed a 20-minute interval sprinting cycling protocol, consisting of repeated bouts of 8-seconds of sprint cycling (at 65% of maximum power output) and 12-seconds of recovery (at 25% of maximum power output), followed by 75 minutes of post-exercise recovery.

    RESULTS: Fat oxidation was significantly greater in the resting condition after green tea ingestion (p < 0.05) compared with the placebo. Fat oxidation was also significantly increased post-exercise in the green tea, compared with the placebo condition (p < 0.01). During and after exercise the plasma glycerol levels significantly increased in both groups after green tea consumption and were significantly higher in the untrained group compared with the trained group (p < 0.05). Compared with the placebo, the plasma epinephrine levels were significantly higher for both groups in the green tea condition during and after exercise, however, norepinephrine levels were only significantly greater, p < 0.05, during and after exercise in the untrained group.

    CONCLUSION: Green tea significantly increased resting and post-exercise fat oxidation and also elevated plasma glycerol and epinephrine levels during and after interval sprinting. Glycerol and norepinephrine levels during interval sprinting were significantly higher in the untrained group compared with the trained group.

    Be well!

    JP

  15. JP Says:

    Updated 10/11/16:

    https://www.cambridge.org/core/journals/british-journal-of-nutrition/article/effects-of-aerobic-exercise-performed-in-fasted-v-fed-state-on-fat-and-carbohydrate-metabolism-in-adults-a-systematic-review-and-meta-analysis/0EA2328A0FF91703C95FD39A38716811

    British Journal of Nutrition, Volume 116 October 2016, pp. 1153-1164

    Effects of aerobic exercise performed in fasted v. fed state on fat and carbohydrate metabolism in adults: a systematic review and meta-analysis

    This study aimed to verify the effect of aerobic exercise performed in the fasted v. fed states on fat and carbohydrate metabolism in adults. Searches were conducted in March 2015, and updated in July 2016, using PubMed®, Scopus and Cochrane databases (terms: ‘fasting’, ‘exercise’, ‘aerobic exercise’, ‘substrate’, ‘energy metabolism’, ‘fat’, ‘glucose’, ‘insulin’ and ‘adult’) and references from selected studies. Trials that compared the metabolic effects of aerobic exercise (duration ≤120 min) performed in the fasted v. fed states in adults were accepted. The outcomes evaluated were fat oxidation during exercise and the plasma concentrations of insulin, glucose and NEFA before and immediately after exercise; two independent reviewers extracted the data (A. F. V. and L. C.). The results were presented as weighted mean differences between treatments, with 95 % CI. Of 10 405 articles identified, twenty-seven studies – with a total of 273 participants – were included. There was a significant increase in fat oxidation during exercise performed in the fasted, compared with fed, state (−3·08 g; 95 % CI −5·38, −0·79; I2 39·1 %). The weighted mean difference of NEFA concentrations was not significantly different between states (0·00 mmol/l; 95 % CI −0·07, 0·08; I2 72·7 %). However, the weighted mean differences of glucose (0·78 mmol/l; 95 % CI 0·43, 1·14; I2 90·8 %) and insulin concentrations (104·5 pmol/l; 95 % CI 70·8, 138·2; I2 94·5 %) were significantly higher for exercise performed in the fed state. We conclude that aerobic exercise performed in the fasted state induces higher fat oxidation than exercise performed in the fed state.

    Be well!

    JP

  16. JP Says:

    Updated 12/17/16:

    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5121695/

    J Clin Diagn Res. 2016 Oct;10(10):KC01-KC06.

    Effect of Integrated Approach of Yoga Therapy on Male Obesity and Psychological Parameters-A Randomised Controlled Trial.

    INTRODUCTION: Obesity is a growing global epidemic and cause of non-communicable diseases. Yoga is one of the effective ways to reduce stress which is one of the causes of obesity.

    AIM: To assess the effect of Integrated Approach of Yoga Therapy (IAYT) yoga module on adult male obesity in an urban setting.

    MATERIALS AND METHODS: RCT (Randomized Controlled Trial) was conducted for 14 weeks on obese male subjects with yoga and control groups. Total number of subjects were 72 and they were randomized into two groups (Yoga n=37, Control n=35). The subjects were from an urban setting of Mumbai and were doing yoga for the first time. Special yoga training of IAYT was given to yoga group for one and half hour for 5 days in a week for 14 weeks. The control group continued regular physical activities and no specific physical activity was given. The assessments were anthropometric parameters of weight, Body Mass Index (BMI), MAC (Mid Upper Arm Circumferences) of Left and Right Arm, Waist Circumference (WC), HC (Hip Circumference), WHR (Waist Hip Ratio), SKF(Skin Fold Thickness of Biceps, Triceps, Sub scapular, suprailiac and cumulative), Percentage body fat based on SKF and Psychological Questionnaires of Perceived Stress Scale (PSS) and AAQW (Acceptance and Action Questionnaire for Weight Related Difficulty). These were taken before and after intervention for both yoga and control groups. Within and between group analysis & correlation of differences from post to pre readings among the variables, were carried out using SPSS 21.

    RESULTS: The anthropometric and psychological parameters were improved in both the groups but changes were significant in yoga group.

    CONCLUSION: Incorporating the IAYT for obese male in urban setting will be effective for obesity treatment and for reducing the obesity related problems.

    Be well!

    JP

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