Hear me out.

So we all know that to lose weight successfully we have to be in a calorie deficit – expending more calories than we take in.

This being said, it would be wise not only to track our calorie intake, but also to get an idea of HOW and WHERE we expend calories in our day-to-day activities. Let’s take the average gym-goer John, who trains for 45-90mins when he hits the gym:

  • Basal metabolic rate (BMR) – This represents Johns daily calorie expenditure required for him to purely exist i.e. lying motionless in bed on an empty stomach, at room temperature. On average this would represent 60-75% of his daily energy output 1,2,3
  • Thermic effect of activity (TEA) – as the name suggests, this is Johns total daily expenditure from his training session. Typically, this will account for around 20% of John’s total daily expenditure1
  • Non-exercise activity thermogenesis (NEAT) – Any movement/exercise outside of John’s scheduled workout performed throughout the day e.g. mowing the lawn, walking to the shop etc. NEAT tends to vary hugely amongst individuals (think waiter/waitress vs any desk job), and is difficult to put a number on, however a good estimate would be 200-400kcals for the average person6
  • Thermic effect of food (TEF) – Lastly, this is John’s daily expenditure from chowing down on some good ol’ grub. This represents around 10% of his expenditure for the day4,5

So, what can we take from this?

Let’s assume John expends, 2300kcals on an average day. From the above, we can deduce that his training-induced expenditure results in a mere 460kcals (20%). Compare this to his BMR related expenditure of 1610kcals and we can begin to see why his training sessions are definitely NOT the most important component when trying to lose weight. For instance, a tall starbucks Caffé Mocha and a Croissant = 600kcals. Easy to see why “I can eat what I want, I’ll burn it all off later in the gym” is flawed. Thus, it is clear that purely in terms of losing weight, we can’t rely on exercise alone.

This is not to say hang up your Lycra quite yet! Rather, I would suggest switching your mind frame in the gym from “I’m gonna smash my session tonight so I can burn loads of fat” to focusing on using your training to improve strength, muscle mass (in turn leading to greater BMR) and health.

Then think of your time outside of the gym (what you put into your mouth) as your key to shedding pounds!

Take home message – Your training session helps in dropping body fat, but not much.

1. Genton L, Melzer K, Pichard C. Energy and macronutrient requirements for physical fitness in exercising subjects. Clin Nutr. 2010;29(4):413–423. doi:10.1016/j.clnu.2010.02.00

2. Shetty P. Energy requirements of adults. Public Health Nutr. 2005;8(7A):994–1009.

3. Ferro-Luzzi A. The conceptual framework for estimating food energy requirement. Public Health Nutr. 2005;8(7A):940–952.

4. Westerterp KR. Diet induced thermogenesis. Nutr Metab (Lond). 2004;1(1):5. doi:10.1186/1743-7075-1-5.

5. Buchholz AC, Schoeller DA. Is a calorie a calorie? Am J Clin Nutr. 2004;79(5):899S–906S. Available at:http://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&id=15113737&retmode=ref&cmd=prlinks.7

6.Levine JA, Lanningham-Foster LM, McCrady SK, et al. Interindividual variation in posture allocation: possible role in human obesity. Science. 2005;307(5709):584–586. doi:10.1126/science.1106561

James Kenny

Personal Trainer Blackheath

Personal Trainer Sevenoaks