Supplementing with whey protein found to improve body fat levels compared to carbohydrate

While protein supplementation can conjure up images of body-building and athlete’s looking to generate power, there is some evidence that it might help mere mortals too. There is quite a body of evidence which suggests, for example, that a bit more protein in the diet can assist with weight loss and weight loss maintenance. See here, here and here for some examples of relevant science.

I was interested to read a recent study which assessed the effect of protein supplementation on weight and other measures, by comparing it to supplementation with carbohydrate. 73 overweight or obese adults were treated with one of three supplements [1]:

  1. whey protein
  2. soy protein
  3. carbohydrate (maltodextrin)

Each supplement provided 400 calories of energy. The supplements were divided between breakfast and dinner. The individuals were instructed to take the supplements but were not advised to make any changes to their diet. The trial lasted 6 months.

Here’s what the results showed:

  • Compared to the carbohydrate-supplemented group, those taking the whey protein supplement were an average of 1.8 kg lighter.
  • Compared to the carbohydrate-supplemented group, those taking the whey protein supplement ended up carrying 2.3 kg less fat.
  • Compared to the carbohydrate-supplemented and soy-supplemented groups, those taking the whey protein supplement ended up with smaller waist circumferences.
  • There were no significant differences between the results seen by those taking soy protein and carbohydrate supplements.

In short, compared to carbohydrate supplementation, whey protein improved weight body fat and waist circumference (larger waist circumference is associated with an increased risk of disease and death).

Before we attempt to explain these differences, it’s worth noting that the addition of the supplements appeared to be compensated for, to a large degree, by consumption of less in terms of the individuals’ normal diets. 400 calories a day equates to 64,000 calories over 23 weeks. There are about 3,500 calories in a pound of fat so, theoretically, the weight gain without any compensation would be around 18 lbs (about 8 kg). This did not happen. Basically, the results showed that the carb group saw a modest increase in weight and body fat, while the whey-supplemented group saw a modest decline in these measures (the soy group pretty much stayed the same).

One obvious explanation for this finding is that whey protein was more satisfying, and led to individuals more than compensating for the addition energy from the supplement in terms of reduced eating of other foods. Consistent with this is the fact that the whey-taking group were found to have lower levels of the appetite-stimulating hormone ghrelin compared to both the other groups.

However, logging of the diets (admittedly not assured to be 100 per cent accurate) revealed the average daily calorie intakes to be:

  1. whey supplemented group – 2183 calories
  2. soy supplemented group – 2267 calories
  3. carbohydrate supplemented group – 2164 calories

So, it does not seem as though the whey-supplemented group ate any less than the carb-supplemented group. Physical activity was monitored, and was found to be the same across the groups.

So, what else might explain the findings? It’s been found that higher protein diets can stimulate the metabolism, and this effect may be mediated through levels of thyroid hormones. There was evidence of this in this study, but most apparent benefit was seen in the group supplemented with soy, suggesting that the better outcomes in the whey group were not largely down to this mechanism.

One other potential explanation for the results concerns the impact of whey and maltodextrin on hormones that control fat stores in the body, especially insulin. Insulin is a hormone that encourages fat deposition. In the protein-supplemented groups, insulin levels were a little lower compared to those in the carb-supplemented group.

The other thing worth bearing in mind is that while protein (like carbohydrate) does stimulate insulin secretion, it also induces he secretion of another hormone too by the name of glucagon. One of glucagon’s effects is to stimulate the release of fat from the fat cells. Also, unlike insulin, glucagon does not stimulate the uptake of sugar into the body’s cells. This helps restrict the amount of glucose available for the production of something called glycerol that is required for the ‘fixing’ of fat in the fat cells.

In other words, while protein increases insulin secretion, the rise in glucagon that comes at the same time mitigates the fat-forming effects of insulin. With carbohydrate, we get insulin secretion that is unopposed by glucagon, with great fat-forming potential to boot.

This study should serve to remind us that the impact that different types of calories have on body fat stores can be different. It also demonstrates that it can be possible to lose fat through a change in dietary composition but without any conscious restriction of calories.


1. Baer DJ, et al. Whey protein but not soy protein supplementation alters body weight and composition in free-living overweight and obese adults. J Nutr. 2011;141(8):1489-94

8 Responses to Supplementing with whey protein found to improve body fat levels compared to carbohydrate

  1. simona 7 October 2011 at 7:15 pm #

    I don’t think that it’s the glycerol, from less glucose.
    From Wikipedia,
    Glucagon raises blood glucose levels. High blood glucose levels stimulate the release of insulin. Insulin allows glucose to be taken up and used by insulin-dependent tissues. Thus, glucagon and insulin are part of a feedback system that keeps blood glucose levels at a stable level.

    Whey is insulinotropic (compared to maltodextrin maybe even more so, but I don’t have the study to point to) and it is useful for muscle repair and formation. Might that be the difference? The 0,5 kg muscle mass?

  2. Jorge Tafich 7 October 2011 at 10:12 pm #

    Dr. Briffa
    I’d like to know your opinion on Don Matesz’s latest post ( about the ability of protein to raise IGF-1 and reduce levels of IGFBP-3. This seems to put protein in a different context.

  3. Victoria 10 October 2011 at 8:46 pm #

    I’m not familiar with the AA structure of the proteins in Whey or soy protein, but could AA signaling (specifically or especially branched chain activation of the mTOR pathway) be responsible for the differences in protein supplements as compared to carbohydrate. An increase in mTOR signaling could lead to an increase in muscle mass, perhaps explaining the difference in weight and fat differences between the carb and whey groups?

    Just a thought…

  4. Julie Craker 10 October 2011 at 11:57 pm #

    Dr. Briffa,
    Whey protein makes you FEEL GOOD with energy to get you through your day. Any of my friends or relatives who finally took my suggestion, some would say naggings, to use it, always have felt better. When I finally learned that we all probably did not get enough protein, (amino acids), I felt it was highly likely this was a big factor in the degenerative processes known as aging and disease. I have since read an article that it actually feeds our DNA and the telomeres that were once thought to be in a constant degenerative process that could not be controlled. I try to vary my amino acid sources with organic protein powders with grain and vegetable sources, not soy, but whey will always be part of my regime.
    Thanks Dr. Briffa for being such a champion for our health. Without doctors such as you to cut through the bad information, I’m putting it nicely, those of us trying to stay healthy through our own means, would have no guiding light.

  5. Kevin eakins 21 October 2011 at 6:39 pm #

    I did not know that protein intake induces raised insulin levels? I thought that insulin was only raised by carbs and that the purpose of insulin was to remove carbs from the blood as quickly as possible for storage them as fat.

  6. Irene @ H.E.S.H. 25 October 2011 at 8:07 pm #

    Thanks for this helpful and informative blog. It can help me to achieve my goal to have a healthier body this year.

  7. ed 28 October 2011 at 9:49 am #

    Dr Briffa,
    I know of someone that consumes these products regularly, is always well hydrated but acquired painful kidney stones. Seems like this isn’t an uncommon situation.

  8. Tom @ 25 September 2012 at 8:41 am #

    I was neglecting whey protein supplementation for years and discovered its benefits not long ago. I don’t see why anyone should acquire kidney stones if stays well hydrated and do not use whey protein extensively. Whey protein is very popular among bodybuilders and other strength and endurance athletes, I never heard of any serious side effects from people who take it responsibly. Thank you fro such a detailed article, Dr Briffa.

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