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PART 3 OF A 4-PART SERIES ON METABOLISM AND WEIGHT LOSS.

Which fitness and lifestyle strategies actually help for weight loss and improving metabolism? 

Without a doubt, we all know that living an active lifestyle is vital to achieving and maintaining a healthy body weight. However, some strategies may be better than others at helping us to get there! This article will specifically review the effects of strength training, high intensity interval training, fasted workouts, sleep, and cold thermogenesis on weight loss and metabolism.

1.  Strength Training:

What is it?

  • Anaerobic training that improves muscular strength by resisting force through the use of free weights, machines, bands, body weight, etc.
  • This type of training is thought to increase muscle strength and lean muscle mass, decrease fat, improve insulin sensitivity, and maintain bone density
  • Excess post workout oxygen consumption (EPOC) or post-burn is often discussed in strength training because you burn more calories AFTER the training session than during (unlike aerobic/cardio training)

What does the research say?

  • There was a study that compared strength, aerobic, or no training in obese dieting individuals (70% of estimated calorie needs through Pro-Cal formula, 1.5g/kg protein) adults for 8 weeks (Geliebter, 1997)
    • Mean weight lost was similar among groups (9kg), but strength group lost less fat free mass 
  • Strength training helps to preserve lean tissue more than aerobic exercise despite the decline in metabolic rate that inevitably occurs with weight loss

My conclusion? 

  • Include strength training into your weekly exercise routine. Aim to incorporate this type of training about 2-3 days per week and include all of the major muscle groups. As you continue losing weight, you will be able to maintain and even gain more muscle mass, which is more metabolically active than fat mass. Overall, you will have a better body composition with strength training and have a higher likelihood of keeping the weight off for the long-run. Need a strength training routine? 

2. High Intensity Interval Training (HIIT):

What is it?

  • Sprint type of training that is typically lesser in volume than aerobic training but with equal metabolic output and endurance gains
  • Most HIIT protocols involve cycling or running for various intervals (i.e. 30-seconds of all out effort, followed by 120-seconds of rest or low-intensity exercise for a total of 15-minutes) 
  • HIIT may also utilize full body exercises and may resemble more of a boot-camp style training 

What does the research say?

  • The Wingate test (30s of all-out maximal cycling repeated 4-6 times separated by 4-minutes of recovery for a total of 2-3 minutes of exercise training performed 3x per week) was studied on healthy, college-aged active men and women. 
    • They found increased muscle oxidative capacity from 15-35% after six sessions of HIIT
    • Changes in carbohydrate metabolism were achieved, similarly to endurance training, with HIIT 

My conclusion? 

  • The most commonly cited reason for not exercising is a “lack of time.” By incorporate HIIT into your weekly exercise routine, you can get the same burn and endurance gains as performing long, slow cardio but without the excessive time commitment. Basically, you can the most bang for your buck when you use HIIT! 

3. Fasted Workouts:

What is it?

  • Exercising after a fast, typically an overnight fast (aka sleeping) of at least 10 hours
  • The type of exercise may vary, but typically includes low to moderate intensity aerobic training like walking, jogging, swimming or cycling 
  • Theoretically, this type of exercise enhances fat utilization due to the lack of glucose stores available for energy burn during the workout 

What does the research say?

  • A study reviewed 20 healthy young females over 4 weeks completing 1 hour of steady-state aerobic exercise 3 days per week, with a calorie deficit diet (Schoenfeld, 2014)
    • Both the fed and fasted group lost weight and fat mass, but no significant between-group differences were noted
  • A study of 19 men split into fasted v fed aerobic training during Ramadan (Trabelsi, 2012)
    • Body weight decreased by 1.9% in the fasted group and 2.6% in fed group, but body fat percentage decreased in fasted group by 6.2%
  • A study of 12 healthy males completing 60min of treadmill running at 70% VO2max in a fed or fasted state, followed by ad libitum (eat as much as you want!) buffet meals 
    • In the group that completed the exercise in a fed state, they experienced prolonged suppression of appetite, but this did not result in any differences in overall energy intake 

My conclusion? 

  • Based on the research I reviewed, it does not appear that consistent results are found when various groups participate in fasted exercise. While theoretically it makes sense that the body would tap into fat stores for energy when it is exercising in a fasted state, this does not seem to translate into research findings. You could consider including 1-2 low to moderate intensity fasted workouts (brisk walking for 30-minutes, yoga for 60-minutes, etc.) into your weekly routine. Do not expect significant results in weight loss. 

4. Sleep:

What is it?

  • Humans spend 1/3 of their lives sleeping!
  • Regulation and metabolism of several hormones are influenced by sleep and circadian rhythm
    • Growth hormone, melatonin, cortisol, leptin, ghrelin
  • According to the National Sleep Foundation, the average sleep duration of American adults was 6h 40min in 2008 compared to 8h 30min in 1960

What does the research say?

  • Longitudinal study investigated sleep duration and visceral adipose tissue (VAT), which is the fat that surrounds the body’s vital organs 
    • Short (<6h) and long (>9h) sleepers gained significantly more VAT than average sleepers
  • Sleep duration and dietary quality was assessed in adolescents
    • Insufficient sleepers exhibited lower diet quality (aka poorer food choices) 
  • Randomized, crossover clinical study measured leptin (the hormone that tells us to stop eating) and ghrelin (the hormone that tells us to start eating) when sleep was restricted to 4h
    • Appetite for high carbohydrate foods was increased by 32%, 18% decrease in leptin, 24% increase in ghrelin and 24% increase in hunger

My conclusion? 

  • If you want to lose weight and keep it off for good, you must prioritize sleep! Aim for 7-9 hours of good quality sleep. This will help with regulation of your hormones and neurotransmitters that help to control appetite, blood sugar, muscle growth, etc. You will have more energy and probably better workouts. Additionally,you will be more likely to choose healthier food options after a good night of sleep. For tips on getting better sleep click here

5. Cold Thermogenesis (CT): 

What is it?

  • Exposure to cold utilizes energy both for shivering and non-shivering functions to help produce heat for the body
    • Include cold exposure with cold showers, cold swims, ice baths, ice packs, cold environmental temperatures, etc. 
  • CT occurs in brown adipose tissue (BAT), which is highly vascularized and metabolically active fat tissue that is controlled by the sympathetic nervous system
    • Think about hibernating animals- they use this mechanism to stay warm
    • Infants have more BAT than older adults (survival mechanism)
    • Lean individuals have more BAT than obese individuals
    • Women have more BAT than men

What does the research say?

  • A small study of 6 healthy men (23-42 years, BMI 23.7-31) exposed to cold and then quantified for BAT oxidative metabolism (Ouellet, 2012)
    • Cold exposure increased BAT and produced an increase in total energy expenditure
    • Inverse relationship between BAT activity and shivering
  • Proponents of this method- Jack Kruse, Ben Greenfield, Tim Ferriss, Mark Sisson

My conclusion?

  • Incorporate daily exposure to cold will help to increase your BAT, which should help to increase total energy expenditure. This means it helps to increase metabolic rate. Significantly? Probably not…but if every little bit counts, then this daily practice could help you over time. Be sure to start slow and to the temperature you can tolerate. Try keeping the home thermostat on low, use a cool-fat burner vest, drink cold fluids, take a cold shower, or even just avoid “over bundling” when you go outside. 

While there was a lot of information reviewed in this article, the key take away points are:

  • Sleep well and enough 
  • Exercise regularly, don’t overthink the type but be sure to include strength training
  • If you do not have time for exercise, use HIIT
  • Expose yourself to cold temperatures daily to boost metabolic rate 

For more tips or help getting started with your weight loss goals start here! 

References:
1.Kim TW, Jeong JH, and Hong SC. Review Article: The Impact of Sleep and Circadian Disturbances on Hormones and Metabolism. International Journal of Endocrinology. 2015;2015:591729.
2. Ouellet V, et al. Brown Adipose Tissue Oxidative Metabolism Contributes to Energy Expenditure During Acute Cold Exposure in Humans. J Clin Invest. 2012;122(2):545-552.
3. Vallerand AL and Jacobs I. Energy Metabolism During Cold Exposure. Int J Sports Med. 1992;13:S191-S193.
4. Geliebter A, et al. Effects of Strength Or Aerobic Training on Body Composition, Resting Metabolic Rate, and Peak Oxygen Consumption in Obese Dieting Subjects. Am J Clin Nutr. 1997;66:557-563.
5. Trabelsi K, et al. Effects of Fed- Versus Fasted- State Aerobic Training During Ramadan on Body Composition and Some Metabolic Parameters in Physically Active Men. International Journal of Sports Nutrition & Exercise Metabolism. 2012;22:11-18.
6. Schoenfeld BJ, et al. Body Composition Changes Associated With Fasted Versus Non-Fasted Aerobic Exercise. Journal of International Society of Sports Nutrition. 2014;11:54.
7. Deighton K, et al. Appetite, Energy Intake and Resting Metabolic Responses to 60-min Treadmill Running Performed in a Fasted Versus a Postprandial State. Appetite. 2012;58:946-954.