Science Catch-up. Low-Carb or Low-Fat For Weight Loss?

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by Alejandra "Alex" Ruani — Get free science updates here.

Welcome to our Thursday’s Science Catch-up: curated links by The Health Sciences Academy. Get our email updates every other Thursday here (it’s free).

Let’s catch you up with studies and news that recently made the headlines!

Click on your favourite topics to read our summary:

1. Low-carb or low-fat for weight loss? Health writers get it wrong (again!)

2. Short sleepers may catch more colds

3. Drinking water before meals leads to weight loss

4. Regular mealtimes make you eat more healthily, study finds

5. Obesity can lead to the alteration of 853 genes

6. For evolving brains, a ‘Paleo’ diet of carbs?

7. Eco-friendly start-up sells ugly fruits and veggies

8. Germany moves to ban genetically modified crops


Low-carb or low-fat for weight loss? Health writers get it wrong (again!)

The BBC announced that low-fat diets are better than cutting carbs for weight loss.

But the Daily Mail wrote: low-carb is best for weight loss. The opposite!

When I dug into these clashing news articles, I noticed they were talking about the same scientific study… Confused?

Well, I was. How is it possible that the journalists concluded the opposite by looking at the same study? Did they even bother to read the full paper?

Probably not. But I did. And here’s what I found:

The study’s low-carb diet (140g carbs + 108g fat a day) led to more weight loss (1.85kg vs 1.3kg), while the low-fat diet (352g carbs + 17g fat a day) led to more fat loss (463g vs 245g).

So the low-carbers lost more weight but less fat, while the low-fatters lost less weight but more fat!

If you carry excess body fat, fat loss is better for your health than just “any” weight loss, e.g. muscle loss.

Just bear in mind that this was a small study with only 19 obese people, locked in a “diet lab”, fed every bite they ate, for 6 days! Not doable in real life, right? Besides, a 6-day outcome can’t predict the effects of following either diet in the long term, no matter how many fancy probability models the scientists run…

Interesting study, though it doesn’t fully settle the low-carb/low-fat debate (sorry!).

Finally, the findings in such a small group of 19 obese people are unlikely to apply to everyone. Individual genetics and biochemistry have a huge impact; and some can tolerate low-carbing better than others. Here’s the full study in PDF format, published in the peer-reviewed journal Cell Metabolism (Hall et al., 2015).

I recently talked about how journalists and health bloggers “spin” headlines; see this list of red flags so you too can spot fabricated information online!


Short sleepers may catch more colds

News link

Another sleep-debt study linking it to poorer immunity. They found that those who sleep less than 5 or 6 hours a night are 4 times more likely to catch a cold than those who get at least 7 hours of sleep. How many hours of sleep have you been getting?


Drinking water before meals leads to weight loss

News link

In this randomised control trial those who drank 500ml of water 30 minutes before their main meals lost more weight (1.3kg) than those who didn’t.

I wrote about water and satiety here, citing a previous “water pre-loading” study with similar findings: 2.3kg extra weight loss for the water pre-loaders across 12 weeks.


Regular mealtimes make you eat more healthily, study finds

News link

This cross-sectional study shows that those who plan their meals ahead and develop regular eating routines tend to eat more vegetables and less fast food or sugary drinks, compared to those who don’t plan ahead or don’t keep an eating routine. Interestingly, those who ate “on the run” or used media while eating ate less healthily. Can you identify with any of this? :-)


Obesity can lead to the alteration of 853 genes

News link

Here’s a little preview about the “dark side of epigenetics”.

Obesity not only changes your body composition but also your DNA (particularly fat-tissue and glandular DNA).

This study identified altered DNA methylation in 853 unique genes (a lot!) that are linked to metabolic disorders, contributing to perturbed insulin and glucagon secretion (e.g. typical in the pathogenesis of Type 2 Diabetes).

Our next question is… are these DNA methylation changes in obese individuals permanent, or can they be reversed if they lose weight? If you love nutrigenetics as much as I do, I recommend you read our recent Science Report From Food to DNA: Can Gene Expression Be Changed?


For evolving brains, a ‘Paleo’ diet of carbs?

News link

The debate continues as to what Paleo humans really ate. This is a provocative review showing that extra copies of the “amylase gene” allowed Paleolithic humans to better digest starches and derive more glucose from them to fuel their evolving brains.

I’ve seen some negative reactions from Ketogenic bloggers, but I can see why. The review focuses on one single aspect and not the full picture like we do in our Science Report Meat-based or Plant Based: What Did Paleo Humans Really Eat?, where Dr Josephine Head (Evolutionary Biologist) and I dive into the scientific record to debunk some myths and misconceptions.


Eco-friendly start-up sells ugly fruits and veggies

News link

I love this idea. These two start-ups rescue “imperfect” fruits and veggies from being trashed by supermarkets (or those that outlasted the “sell-by” date but are perfectly edible), and repackage them at much lower prices so low-income families or bargain-loving shoppers can also access healthier options.

It’d be great to see more start-ups like these around. Wasted food is a huge issue in developed countries, and let’s not forget about the environmental impact from the water and fuel used to produce and ship that food.


Germany moves to ban genetically modified crops

News link

Although many GMO varieties have been approved as “safe” by the European Commission in March this year (2015), European countries have the right to “opt out” and ban GMO cultivation on their soil.

Countries have until 3rd October to opt out, so we’re getting closer! Who else might follow Germany?

GMO can be an emotional topic for many, which causes a lot of fear and anxiety. So, we’re currently working on an objective “mountain-top” review of the current scientific evidence on GMOs. Keep an eye out for this special Science Report – I haven’t seen anything as comprehensive and unbiased to date.



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What has inspired you this week? What are your thoughts on some of these topics? Leave a comment and let us know!

Alex Ruani leads the research division at The Health Sciences Academy, where she and her team make sense of complex scientific literature and translate it into easy-to-understand practical concepts for students. She is a Harvard-trained scientific researcher who specialises in cravings and appetite neurobiology, nutrition biochemistry, and nutrigenomics. Besides investigating and teaching the latest advances in health and nutrition science, Alex makes it easier to be smarter with her free Science Catch-ups every other Thursday.
Connect with Alex via email.

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  • Shigufta

    Reply Reply September 10, 2015

    I love reading about health and science! The best part is, the reasearch is evidence based which is a bonus. No one likes to read an exciting piece of health news only to find, there is no data or referencing. Thank you!

  • Cynthia

    Reply Reply September 10, 2015

    It is nice to read with the assurance of fact and not fiction. Thanks for your diligence.

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