When I say dieting in the title, I mean extended periods of low calories – i.e. the typical 12-24 week diet, or even perma-diet for some.
A hypocaloric state is catabolic, meaning tissues are broken down from both fat and muscle. This is not necessarily a bad thing. When you’re catabolic you break down both lipids and proteins, i.e. both fat AND muscle in varying amounts. See this study - large calorie deficits associated with drop in testosterone, creating a catabolic hormonal environment, worse mood, and more risk of muscle and strength loss. The trick when dieting is to oxidise as much fat as possible while oxidising as little protein as possible.
So how do we do this?
When you cycle periods of overfeeding and underfeeding, you’re creating waves of anabolism (where you gain some muscle and some fat) and catabolism (where you lose some muscle and fat). Despite this, if the total calorie balance at the end of the week is a deficit, there is a net fat loss effect, while avoiding the negative effects outlined above.
By taking certain anti-catabolic measures you can spare as much muscle tissue as possible while burning as much fat as possible during the underfeeding phase:
- Sufficient protein intake: 2g per kg bodyweight
- Heavy resistance training 3-4x/week
- Skipping breakfast
- Fasted walking
- Keeping carbs low on rest days
- After training, eating your carbs at night
- Medium Chain Triglycerides (MCT) to promote ketone production and spare muscle tissue
^ Sound familiar? :P
By taking the same measures you can also gain as much muscle tissue as possible while generating as little fat tissue as possible.
- A high carb, low fat refeed after training (up to 4-5g carbs per kg bodyweight)
- Moderate volume training
- Sleeping a minimum of 7.5 hours per night
- Staying well hydrated (Don’t overlook this one. Cellular dehydration is very catabolic)
Fortunately, by following those guidelines, we don’t have to gain 50:50 muscle:fat all the time like some people would have you believe (not mentioning any names here), where you bulk for years while getting fat as hell, then cut for 6 months and lose half of your hard earned muscle. Instead, do this correctly and the net effect can mean you actually gain muscle while losing fat as the weeks go by.
What if I just want to lose fat at all costs?
Fine, but underfeeding for extended periods causes a drop in BMR. So you’ll have to eat less and less as the weeks go on. Additionally, testosterone and other growth factors drop off, which is associated with depression and lethargy.
Also – fasting allows you to confine your eating window to a shorter period, reducing your meal frequency. This has the benefit of allowing the fasted state to remain uninterrupted for longer:
Berkhan is passionate about meal frequency, and points out that a lower meal frequency is better from a neurobiological, blood sugar control, appetite and metabolic perspective. There is an increased thermogenic response from lower meal frequency, and a metabolic decrease in the long term from high meal frequency (nibbling). So let’s put this 6-meals-a-day idea to rest. It’s inconvenient, and at the very least the evidence shows no benefit.
Why periodic overfeeds are better:
The underfeed followed by an overfeed sensitises your body to insulin, and revs up the metabolism. If you cut calories quickly enough while your body is in that state, metabolism stays elevated while there are no calories available to feed it. The body turns to fat stores for fuel. Better still, if you fast, the growth hormone release will bump metabolism up even further while sparing muscle tissue. Growth hormone is one of the most powerful lipolytic yet muscle sparing hormones in the body.
From Kiefer’s Carb Nite book:
Appetite and metabolism are tightly regulated by ghrelin and leptin, hunger and fullness hormones. Overfeeding causes a delayed rise in leptin and a concomitant increase in metabolism and fat loss. Fortunately it’s a lagging hormone, so leptin will stay elevated for longer than your overfeed period, and stay elevated for around 4 days (varies according to individual).
Hence while you’re fasting immediately after an overfeed, BMR and fat loss will be through the roof. Additionally, fasting allows fat mobilisation to continue without being mediated by leptin. By continuing to cycle overfeeds and underfeeds over the week as we’ve described, leptin will be elevated frequently enough to keep metabolism high.
To take it to the extreme, it would be far superior to eat like this:
Even though the average calories are the same. The above is an extreme example, but which do you think you’d enjoy more? Constant deprivation or periodic feasts? Worse still would be eating 1000kcal per day for months on end, chronically underfed, fatigued, pissed off and plummeting your metabolism. This is why we advise periodic 24 hour or even alternate day fasting, which makes dieting a lot more tolerable.
What if I don’t want to fast for that long?
Leangains-style intermittent fasting of a 16-hour fast followed by an 8-hour eating window would be ideal in this case. Cycle your calories and your carbs throughout the week and receive the same benefits.
Putting it all together:
Extreme, extended diets, despite making you feel deprived and awful, actually cause a reduction in metabolic rate and make fat loss more difficult. So it’s actually optimal to cycle periods of overfeeding and underfeeding (and/or fasting) to gain muscle and lose fat. This is ideal for pure fat loss even if you’re not interested in gaining as much muscle as possible. You’ll be getting the best of both worlds:
• High growth hormone output from the fast, sparing muscle tissue
• No drop in testosterone levels that you would normally get from extended dieting
• No more tiny portions of broccoli and muesli, when you eat, you eat big.
• Ramped up metabolic rate from the overfeeding periods, lasting well into the fast.