Over the many years I’ve been involved in the fat loss game, I’ve seen some weird stuff happen. When I was in my 20’s and only thought I knew what I was talking about (as opposed to now when I’m simply usually sure I do), I had observed one of the things I’m going to talk about today but didn’t have any real clue why it happened. With clients or whatever, the only answer I could give was “Because it does.” or “Magic!”.
Now, I have a bit more clue what’s going on, or at least what I think is going on so I’m going to share one of these with you (I’ll address others in future articles). Today I want to talk about something that I like to call the LTDFLE, an acronym that I genuinely hope you will use at every possible chance on forums to confuse people, and which will make sense shortly.
Anyone who has had the headache-inducing misfortune of reading (or trying to read) Supertraining by Mel Siff and Yuri Verkoshansky may have a clue where I’m going with this section heading. In that book, one topic that is discussed rather endlessly is the long-term delayed training effect (LTDTE), a phenomenon whereby strength/performance gains often show up considerably (e.g. 2-4 weeks) after the heavy training has been done. This can actually be explained fairly simply through a two-model fitness/fatigue theory of adaptation but I’m getting way off track.
LTDFLE stands for Long-Term Delayed Fat Loss Effect (I’d note that I have also seen a LTDGE which is a Long-Term Delayed Growth Effect but that’s another topic for another article). Basically, this is the phenomenon whereby fat loss continues to occur even after the diet has been ended and/or calories have been raised back towards/to maintenance or even above. In the same way that fitness sometimes continues to increase after the period of heavy loading, it’s almost as if there is some type of fat loss inertia whereby the diet continues working even after the person ends it.
Now, I talked about a similar phenomenon in the article Of Whooshes and Squishy Fat, a situation where, usually after the diet is broken (for a meal or a day), folks often wake up lighter and leaner. But that’s more of an acute thing that I think can clearly be related to water retention/the release of such that happens when people break their diets (deliberately or otherwise).
The LTDFLE is a bit different and can last from 4-7 days (on average). During that time, and note that this only happens after fairly prolonged dieting, as calories are brought up, people continue to get visibly and measurably leaner. Skinfolds continue to drop, other measurements will continue to change in the direction of a decreased body fat.
I’ve observed the LTDFLE in myself, in trainees/clients and it’s something that a lot of bodybuilders (depending on how nuts they go) experience in the first few days after a show. After all that work, after all that effort, they end up looking their best 2-3 days after the post-contest binge has started.
In fact, there’s actually even a weird study from back in the late-90’s that saw this although the researchers had no clue what was actually going on (because nutrition researchers don’t read enough basic science/endocrinology). In it, folks were dieted hard for 4 weeks and then progressively refed (raising calories over the 5th week towards maintenance). Body weight kept going down in Week 5 despite the gradually increasing calories (as I recall, they didn’t measure body composition).
What’s Going On?
Now, it seems fairly obvious that at least some of the LTDFLE is due to water retention and water balances, just like the acute whooshes discussed in Of Whooshes and Squishy Fat. Although there is a great deal of variance, people often retain water (both under the skin and possibly within fat cells) when they are dieting hard and restricting calories and much of this is related to increases in the hormone cortisol (please note that water retention is profoundly more complicated than this). Raising calories/carbohydrates and/or reducing training tends to shut down cortisol release. Suddenly the body stops freaking out and water is dropped. But I wouldn’t expect water loss to explain a full week of visual changes. A day, maybe two, sure. But not the 4-7 days that the LTDFLE typically runs.
An additional factor that is certainly involved, and especially with folks on low-carbohydrate diets who are doing a lot of training, is replenishing muscle glycogen. As carbs are raised, the body starts sucking up carbs (this has an additional effect of pulling water into muscle which probably also accounts for water shifts), they fill out and start to look better. This is assuredly a big part of why bodybuilders often look better 2 days after their show; instead of looking stringy and flat on stage, they get full and pumped. If water is being dropped from the body at the same time, all the better from a visible standpoint. Please note that muscle glycogen is only increased if the caloric increase comes from carbohdyrates; pigging out on high-fat fare won’t get it done.
Of course, the increase in glycogen/water mediated lean body mass will have a small effect on actual body fat percentage but, as discussed in Reducing Bodyfat by Gaining Muscle – Q&A, the effect is not large. It doesn’t hurt, of course, but it certainly doesn’t explain all of it.
But even with that, it does seem that actual fat is still being lost, skinfolds get measurably smaller and people look leaner (and depending on what’s done next, often the skinfolds stay down suggesting that it’s more than just a transient water shift magic trick). So beyond the above explanations, what’s really going on. I suspect that at least some of it is related to leptin kinetics. If you’re not familiar with leptin and what it does, I’d suggest you take the time to read the 6-part series on Bodyweight Regulation: Leptin. I’ll wait.
As I’ve discussed in my various books and in the article The Full Diet Break, leptin starts to increase fairly quickly when calories and carbohydrates are raised, even 5 hours of over-eating carbs can raise leptin. With even a few days of eating more calories/carbs, leptin will go up. And while many of the effects of leptin aren’t immediate (which is part of why I recommend 10-14 days for a full diet break), some of them might be.
Leptin is part of what regulates cortisol levels for example (leptin inhibits cortisol release) so at the very least, increasing leptin would help to reduce water retention. But some work has also shown a direct effect of leptin on fat cells in terms of lipolysis; leptin also promotes fat oxidation in skeletal muscle and elsewhere, perhaps the increase in leptin is directly stimulating actual fat loss. Of course, that explanation is predicated on leptin going up/having a greater impact on things than the excess of calories coming in has on fat gain.
Related to that are thyroid hormone kinetics. On a diet, conversion of the relatively inactive T4 to the more active T3 goes down in the liver and this rebounds fairly quickly when calories (and especially carbohydrates) are raised. Tangentially, this is why I recommend a minimum of 100-150 grams of carbohydrates per day during a The Full Diet Break; that’s what is required to normalize T3 production in the liver. As well, leptin is involved in the control of thyroid stimulating hormone (TSH) so increasing leptin may also be driving thyroid output.
Now, T3 has both short-term and long-term effects on metabolism with most of the long-term effects being related to changes in gene expression; those take time to maximally occur (at least 14 days). But T3 can also be degraded to T2 which has immediate metabolic effects on energy expenditure and it seems possible that increases in T3 and subsequent breakdown to T2 might be raising metabolic rate enough to not only offset the increased calories but also to generate extra fat loss. That might explain part of the LTDFLE as well.
I mentioned gene expression above, this is just a nerd term referring to changes in which genes are turned ‘on’ or ‘off’ (simplistically speaking) in various cells. And gene expression changes in response to dieting, caloric intake, activity, etc. While some changes happen pretty quickly others take longer; it’s not an instantaneous process. Many have observed that often a diet takes a solid week or so to start ‘working’ and this may be related to slower changes in gene expression when someone moves from an above maintenance caloric intake to a below maintenance caloric intake.
And the same may be working in reverse, the body is still effectively in a ‘fat burning mode’ for some period of time after calories are raised. Along with any direct effects of leptin and/or thyroid on lipolysis/fat oxidation/metabolic rate and the shifts in water balance, the situation is still simply this: people often keep getting leaner in the first week off their diet (again, this assumes that they don’t go totally nuts with food intake).
I’d note in this regards that my own Ultimate Diet 2.0 actually takes advantage of this to get a short-term sidestep of the energy balance equation: for about 24 hours following the 4 hard days of dieting/glycogen depletion, even in the face of massive carbohydrate intake, the body preferentially stores the incoming carbs as glycogen while using fatty acids for fuel (part of why fat intake has to be kept low during the carb-load). Folks may be at literally double maintenance caloric intake and still be losing fat. Magic? No, just good science. Ok, maybe a little magic.
And that’s the oddity that is the LTDFLE: that magic period where, despite raising calories, you keep leaning out and losing fat. It’s only about 7 days at the longest and can be shorter if people go really nuts with their food intake. This is especially true if a lot of high-fat foods are consumed for extended periods. Empirically, making the LTDFLE work the best seems to involve raising carbohydrate intake moreso than dietary fat. In that vein, in the short-term 2-3 days), leptin levels are only responsive to increasing dietary carbohydrate intake, not fat.
So that’s the LTDFLE, an oddity of fat loss that tends to occur after fairly prolonged dieting when calories are raised. It’s not universal and doesn’t always happen but when it does, enjoy it. Before I finish, let me make one thing very clear which is that the LTDFLE only occurs after fairly prolonged actual dieting (which can still contain free meals and refeeds as discussed in A Guide to Flexible Dieting). Don’t think that you’re going to get the magic effect of the LTDFLE by half-assing it for a couple of weeks and then raising calories and voila.
In a future article, I’ll look at another specific oddity of fat loss, the situation where combining a large caloric deficit with too much activity can actually hurt rather than help weight/fat loss. But that’s for another day.
- All Diets Work: Qualification
- Bodyweight Regulation: Leptin Part 3
- The 3500 Calorie Rule
- Bodyweight Regulation: Leptin Part 5
- Bodyweight Regulation: Leptin Part 2