3. How To Keep Your Weight Off - Adaptive Thermogenesis Made Simple
Updated: Apr 8
So in the first post, I mentioned a healthy life is a choice and there are things you can do to prevent weight-related chronic problems. In the last post, we discussed the composition of energy expenditure, what adaptive thermogenesis (AT) is and why weight loss is hard to achieve by dieting alone.
Indeed, AT is a blindspot we need to check before making a conscious change in lifestyle to achieve weight loss.
Tough ain't enough. You've got be smart as well! Here is some quick actionable information and an interesting video!
1. What is AT?
AT is a variable amount of heat generation in basal metabolic rate, typically measured in kcal/day. To be slightly more technical, AT is the change in basal metabolic rate (BMR) in addition to the part accounted for by the changes in body composition. It exists in both animals and humans.
2. Who should pay attention?
Anyone who plans to lose/gain weight, or to keep the weight off after weight loss.
3. How much is it?
It is about 14% of the basal metabolic rate. For a 70kg adult man, it is about 250 kcal/day. AT varies from individual to individual and it can be much higher than 250 kcal/day.
4. How was AT discovered?
It was first reported by a french scientist Neumann in 1902. The clinical significance of AT was disputed in much of the 20th century, until compelling clinical evidence was established in the mid-90’s .
5. How is AT regulated?
AT is regulated by the brain, controlled via different diffusive factors, including neuropeptides and leptin, an adipocyte-derived hormone.
6. What are the influencing factors?
AT is influenced by dietary and environmental factors.
Starvation reduces leptin to decrease thermogenesis by the brown fat cells.
The brain senses cold temperature and increases thermogenesis mainly by innovating brown adipose tissue and skeletal muscle.
Organochlorines (OCs) are a type of chemical pollutant. They reduce thyroid hormone in models, decrease skeletal muscle oxidative potential and inhibit mitochondrial electron transport. The levels of OCs in blood plasma have been found to be associated with reduction in resting metabolic rate.
7. When does it matter?
AT become significant in humans after weight loss due to changes in diet and physical activity, and it underpins weight regain [2, 3].
For instance, a 2016 study by the National Institute of Health in Bethesda, Maryland tracked participants of “The Biggest Loser” competition 6 years afterwards. Mean age 35 and mean body weight 149kg initially, 91kg at the end of the competition at week 30, and 132kg 6 years afterwards. The scientists found a whopping 500 kcal/day AT on average. In other words, 6 years after the TV programme, the Resting Metabolic Rate (RMR) of a participant is on average 500 kcal/day less than a person of the same age, gender and body composition. Since the participants burn less calories, they regained weight .
8. How do I know if AT affects me?
Don’t guess. Measure! This is recommended by researchers in the field for people who have gone through weight loss attempts previously.
You can measure Resting Metabolic Rate (RMR), an approximate of your Basal Metabolic Rate (BMR) quantified using a less stringent procedure, by using indirect calorimetry. This is a test taking approximately half an hour to complete and involves you wearing a breathing mask whilst seated at rest, to collect and analyse expired air. It costs you about £40.
9. What can I do about AT?
Once you’ve measured your RMR, you can put it into a mathematical model to calculate how much energy intake and activity you need to achieve what weight loss/gain goal in what time.
If you have not measured you RMR, you can still use phd-fitness.com as your physiology will be mimicked by the population average.
10. How can PhD Fitness help?
We treat your AT at the population average to begin with. When you use the planning tool, a clinically validated model is used to simulate how AT changes over time given your planned calories intake and physical activities, hence to figure out how much body weight change you would see.
An exciting feature we are developing is to figure our your own AT for you without measuring your RMR using indirect calorimetry. This would require your historical calories intake and physical activity (wearable device) data.
Now you clearly see why it is very hard to starve yourself to a normal BMI. In fact, sustainable weight loss can never by achieved by calorie-restricted diets alone.
The only part of energy expenditure in your control is physical activity. Next week, we will introduce physical activity level, a critical measure of your life, to ensure you live a healthy one that is PAL1.7.
1. Leibel RL, et al. Changes in energy expenditure resulting from altered body weight. N. Engl. J. Med. 332(10): 621–628 (1995).
2. Tremblay A, et al. Role of Adaptive Thermogenesis in Unsuccessful Weight-Loss Intervention. Future Lipidology. 2(6): 651-658 (2007).
3. Major GC, et al. Clinical significance of adaptive thermogenesis. Int J Obes (Lond). 31(2): 204-12 (2007).
4. Fothergill E, et al. Persistent Metabolic Adaptation 6 Years After “The Biggest Loser” Competition. Obesity. 24(8):1612-9 (2016).