Can we STILL grow muscle when dieting?

Posted by Dayne Hudson in Muscle Building

Estimated reading time: 5mins

Can we STILL grow muscle when dieting?
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Growing muscle in a calorie deficit

Here’s a sad fact: pumping iron in a calorie deficit hinders the production of insulin-like growth factor-1 (IGF-1).

IGF1 is a hormone that supports muscle growth, with other research revealing impaired muscle growth responses to resistance training with just three days in a calorie deficit!

Growth hormone is also impaired, which is critical for a number of muscle-building happenings (which IGF-1 also helps with) such as protein metabolism.

So, you can see why training in a calorie deficit for muscle growth isn’t ideal.

But a new review HAS found something worth smiling about: strength gains aren’t impaired by an energy deficit!

Now, some experienced lifters will be able to tell you this – when they start dieting, their strength gains can still go up.

The authors say this might mean that strength gains are independent of muscle growth and instead due to neural adaptations.

I notice strength gains when dieting, so it’s great to see it confirmed in reviews.

On this website, and to those I work with, I recommend a 500-calorie deficit for weight loss. And this review also found that this precise deficit stopped the growth of muscle combined with weight training.

But it’s just confirming what we already know.

But what the review also found was a 500-calorie deficit is a sweet spot for maintaining muscle and losing fat – as long as you keep lifting weights.

Now that’s reassuring.

In a brief summary, the new review found:

  • Resistance training in a calorie deficit impairs muscle gains, but not strength, compared to those lifting weights WITHOUT a deficit of calories
  • The common energy deficit of 500 calories a day was sufficient to prevent gains in muscle from weight lifting – BUT
  • Those looking to lose weight and maintain muscle (whilst still lifting) should eat in a 500-calorie deficit or less (but not more).

So, this part is important: keep your deficit at 500 calories and keep lifting weights when dieting to preserve your hard-earned muscle.

Keep lifting weights in a calorie deficit to preserve muscle mass.
Keep lifting weights in a calorie deficit to preserve muscle mass.

A lot of lifters can get really aggressive with their deficits and can go as far as an 800-calorie deficit. This will really put your muscle gains at risk.

But the review authors admit that protein intake wasn’t accounted for. So you can take this two different ways:

  1. “Screw it, if I eat more protein, I can have a higher deficit.”
  2. “I’ll be cautious, and stick to a 500 calorie deficit only in light of these findings.”

A recent study into bodybuilders and athletes found they can go as high as 3.1 grams of protein per kilogram of fat-free mass. This is critical for protecting your muscle.

So, you might want to try this if you’re eating in a deficit greater than 500 calories.

But the fact remains that losing fat at a slower rate seems to be better for muscle preservation.

This study found those who want to gain muscle and increase strength whilst dieting and lifting weights, should aim for a weekly body weight loss of 0.7%.

This was compared to a group who were losing weight at 1.4%.

Body Builder

But can we still grow muscle in a deficit?

If you’re new to weightlifting, yes.

Let’s say you’re overweight, lifting weights, and eating in a calorie deficit.

Now, as the study link above shows, you CAN grow muscle in a deficit.

But how?

Well, because your fat stores can provide the energy that your absent calorie surplus is not.

So, the new person at the gym drastically overweight can lose fat AND gain muscle whilst in a surplus because they have:

  • The fat stores to make up for it
  • Their muscles are untrained and will respond quicker

But what about the person who is around 10 per cent body fat, has been lifting for 9 years, and is in a calorie deficit?

As the featured study of this study illustrates, it’s not likely whatsoever.

That’s why for experienced lifters, the advice is still the same: eat in a surplus when muscle growth is the goal and eat in a deficit of 500 calories for slow and steady fat loss to not risk muscle loss.

Don’t diet higher than a 500 calorie deficit – you’ll risk muscle loss.
Don’t diet higher than a 500 calorie deficit – you’ll risk muscle loss.

The bottom line on still growing muscle when dieting

Is that experienced lifters can still see strength gains in a 500-calorie deficit, but not muscle growth. Experienced lifters must have a high protein intake during a diet, and ensure they keep lifting weights; both these measures will help preserve lean muscle mass.

Those new to weight lifting can grow muscle and lose fat at the same time because they can use their fat stores to make up the energy gap from their calorie deficit, and their muscles are untrained and respond more.

For experienced lifters, the advice is still the same: eat in a surplus when muscle growth is the goal and eat in a deficit of 500 calories for slow and steady fat loss to not risk muscle loss.

References:

  1. Clemmons DR. Metabolic actions of insulin-like growth factor-I in normal physiology and diabetes. Endocrinol Metab Clin North Am. 2012;41(2):425-443. https://doi.org/10.1016/j.ecl.2012.04.017
  2. Donnelly JE, Sharp T, Houmard J, Carlson MG, Hill JO, Whatley JE, Israel RG. Muscle hypertrophy with large-scale weight loss and resistance training. Am J Clin Nutr. 1993 Oct;58(4):561-5. doi: 10.1093/ajcn/58.4.561. PMID: 8379514.
  3. Ecl.2012.04.017
  4. Folland JP, Williams AG. The adaptations to strength training : morphological and neurological contributions to increased strength. Sports Med. 2007;37(2):145-168. https://doi.org/10.2165/00007256-200737020-00004
  5. Garthe I, Raastad T, Refsnes PE, Koivisto A, Sundgot-Borgen J. Effect of two different weight-loss rates on body composition and strength and power-related performance in elite athletes. Int J Sport NutrExercMetab. 2011 Apr;21(2):97-104. doi: 10.1123/ijsnem.21.2.97. PMID: 21558571.
  6. Helms ER, Zinn C, Rowlands DS, Brown SR. A systematic review of dietary protein during caloric restriction in resistance trained lean athletes: a case for higher intakes. Int J Sport NutrExercMetab. 2014 Apr;24(2):127-38. doi: 10.1123/ijsnem.2013-0054. Epub 2013 Oct 2. PMID: 24092765.
  7. Moller N, Jorgensen JO. Effects of growth hormone on glucose,lipid, and protein metabolism in human subjects. Endocr Rev. 2009;30(2):152-177. https://doi.org/10.1210/er.2008-0027
  8. Murphy C, Koehler K. Caloric restriction induces anabolic resistance to resistance exercise. Eur J Appl Physiol. 2020;120(5):1155-1164. https://doi.org/10.1007/s00421-020-04354-0
  9. Murphy C, Koehler K. Energy deficiency impairs resistance training gains in lean mass but not strength: A meta-analysis and meta-regression. Scand J Med Sci Sports. 2022 Jan;32(1):125-137. doi: 10.1111/sms.14075. Epub 2021 Oct 13. PMID: 34623696.

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