When we discuss fat loss at Triage, we often place "calories in vs calories out" or "energy balance" at the centre. But, this can often be misinterpreted to mean that weight loss will occur linearly each week once you just reduce your calories. There is far more to the story, which we will begin to unpack in
this email.
To set the stage, yes, the primary determinant of whether you lose or gain weight over time is energy balance (or energy imbalance really!). If energy intake is in excess of energy output, bodyweight will increase, and vice versa if output exceeds intake. However, there is more to it than that.
Body Weight vs Body Composition: Weight =/= Fat
The largest compartment of energy in the body is adipose tissue (fat), which is why it's the central focus of discussions related to weight change. There are other
compartments that can increase or decrease in response to changes in energy and other dietary factors, including muscle, water, bone, intramuscular carbohydrate stores, food contents in the gut, and a couple of other minor contributors.
This matters because you may misinterpret a change in weight if you are not aware of how these compartments change. For example, water
retention and digestion can vary throughout a woman's menstrual cycle, with considerable inter-individual variability. If we take the 'textbook' case, a woman is likely to see her weight increase prior to her period, which could be misinterpreted as an energy surplus. The inexperienced coach or nutritionist would then encourage her to reduce her calories further, when in fact, this may only make her diet more difficult to sustain during this time (reducing calories when cravings & hunger are
highest for some women probably isn't the best decision).
Individual Triage Client Case: Not all women will respond the same, but observing
these trends assists with decision-making. Note the peaks & troughs and focus on the trend!
Another common example we see in practice relates to carbohydrate vs calorie reduction. If two people go on a diet at the same caloric intake, but one consumes a low carb diet, the person on the low carb diet will rapidly lose weight in the first couple of
weeks. This is primarily due to reductions in glycogen & water weight, which can lead people to feel this is the best way for them to lose weight. However, when you follow the diets over time, there's no significant difference, as what was seen in those first couple of weeks was not accelerated fat loss.
There are many more examples to flesh out (e.g. protein +
resistance training impacts body composition in a way that goes beyond just calories), which are covered in more depth in the Triage Nutrition Course.
Metabolic Adaptation: "Starvation Mode"?
When calories are reduced, the body begins to adapt to this intake over time. Some people think that the body goes into a form of 'starvation mode' where they can gain fat despite being in an energy deficit, which isn't true. But, that doesn't mean there are no adaptations taking place
to starvation, as there are.
The first key point to cover here is that a lighter body burns less energy. People often forget this and jump straight to cellular adaptations, but this is a huge factor. If we take the example of someone that diets from 100kg to 75kg, they have now lost 25% of their bodyweight. Not only is this metabolically active tissue (even fat is
metabolically active, albeit to a much lesser extent than other tissues) no longer present, but it's also like removing a 25kg weighted vest. When you consider that bodybuilders sometimes wear weighted vests to burn more calories throughout the day, you can appreciate that this is a significant effect. Therefore, if you diet down and lose a significant amount of weight, you should expect your maintenance calories to now be lower, unless you are more active or significantly more muscular, of
course.
That brings us to the note of activity. Sometimes consciously, and sometimes unconsciously, your body will begin to get a little more sluggish as you diet down. This may manifest as you walking less, being less willing to take the stairs, and not being quite as enthusiastic about other non-exercise activity. Or, it may manifest more subtilely with less
fidgeting, blinking, or a more slumped posture. This is one of the reasons we often suggest that people track their steps when dieting, as this can assist with maintaining "Non Exercise Activity Thermogenesis" (NEAT), compensating for some of the expected reductions in energy expenditure. We have a great video on this topic here.
There are also cellular adaptations that occur, such as reduced
uncoupling at the level of the mitochondria. This means that less energy is wasted, and is part of why you often feel more cold when dieting, especially after a long period in a deficit (there are other factors, such as reductions in thyroid hormones and less physical insulation via body fat). Again, more of these technical details are covered in the coursefor those who want to get stuck in to understanding these concepts deeper (see graphic above).
If you like this topic and want to learn more for free, you can start with the following educational material we have produced:
