Science Catch-up. Study Highlights Which Fruits and Vegetables Can Aid 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. Study highlights which fruits and vegetables can aid weight loss

2. Coffee consumption ‘does not raise risk for common form of irregular heartbeat’

3. How to teach… sugar?

4. Cocoa flavonols good, but chocolate not?

5. Paleo nutrition for metabolic syndrome?

6. Beans match beef for satiety – but consumers don’t expect it to

 

Study highlights which fruits and vegetables can aid weight loss

When most health messages highlight the generic benefits of fruits and vegetables, what I like about this one is that it compared 70 of them in relation to body weight changes.

This huge observational study followed the diets of 133,468 men and women for 24 years. It looked at their consumption of 70 unprocessed fruits and vegetables in relation to their body weight. Here’s what they found:

  • When the participants increased their intake of higher-fibre, non-starchy, lower-glycaemic vegetables, particularly cruciferous vegetables like broccoli and Brussels sprouts, their weight went down: 0.25 lbs (0.11kg) of body weight per daily serving over 4 years.
  • Whole fruits (not juices), mainly berries, apples and pears, which are low-glycaemic, contributed to greater weight loss: 0.53 lbs (0.24kg) per daily serving over 4 years.

High-fibre, non-starchy, low-glycaemic vegetables are quite filling and you can eat bigger portions of these foods without feeling deprived. They’re great if you enjoy eating until complete satiation, like I do (Italian genes!).

Here’s the full study: Changes in intake of fruits and vegetables and weight change in United States men and women followed for up to 24 years: analysis from three prospective cohort studies, Bertoia et al., 2015. PLOS Medicine.

 

Coffee consumption ‘does not raise risk for common form of irregular heartbeat’

News link

This is one of those studies where I think the scientists love their coffee (!). In this trial involving 248,910 individuals, they didn’t find any link between coffee intake and atrial fibrillation.

Atrial fibrillation is a “common form” of irregular heartbeat (arrhythmia) that this news headline didn’t mention. But that’s not the only form of arrhythmia, so this study cannot prove that coffee won’t cause “other” kinds of arrhythmia.

At the end of the day, we all metabolise coffee differently (some faster than others) and it has a lot to do with your genetics. You can learn more here: Nutrigenomics 101: Coffee and Your Genes (premium subscription needed).

 

How to teach… sugar?

News link

I think this is a great list of resources if you’re trying to raise awareness about added sugars. I particularly liked the downloads at British Sugar, including PowerPoint presentations, worksheets, and scientific experiments for schools. Here’s the British Sugar link.

 

Cocoa flavonols good, but chocolate not?

This is hilarious and I could not resist sharing it with you.

A Science Daily headline says: “Cocoa flavanols lower blood pressure and increase blood vessel function in healthy people”.

But this other headline bursts the bubble: “Chocolate “unsuitable” for cocoa flavanol delivery despite new heart health pros, says Mars-backed consortium”.

In essence, they are talking about the same study. It appears that cocoa flavanols are tied to lowering blood pressure and heart disease risk in healthy people. However, the scientists said that chocolate is too calorific to “safely” deliver the same amount of concentrated cocoa flavonols used in the study: 450mg a day.

I ran some numbers and this means you’d need to eat 414 to 841 grams of dark chocolate daily. That’s around 2260 to 4592 calories a day of chocolate, alone! So Mars are now looking at creating a “super chocolate”, with more cocoa flavonols in it. This is going to be tough to achieve, because much of these flavonols are destroyed during processing. In the meantime, you can stick to raw chocolate – if it’s the flavonols that you’re after!

 

Paleo nutrition for metabolic syndrome?

Study link

There isn’t much research about our “modern-day” Paleo diet and this systematic review pulls the data from 4 studies. Each of these 4 studies used different Paleo diet plans, so it’s difficult to compare the results like-for-like. Although the review highlights some benefits, the studies were short-term.

All 4 included meat, but we know of some Paleolithic ancestors who ate mostly plant-based foods. Here’s how scientists can tell when ancestral diets were plant-based or meat-based: Plant-Based or Meat-Based: What Did Paleo Humans Really Eat? (premium subscription needed).

 

Beans match beef for satiety – but consumers don’t expect it to

News link

Here’s an interesting one for those who believe that animal protein is more satiating. It appears that beans match meat for satiety because of their blend of both protein and fibre. As we know, meat doesn’t contain any fibre. Besides being high-fibre, beans are low-glycaemic – all of which play a role in appetite suppression.

 

 

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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!

The-Health-Sciences-Academy-Alejandra-Ruani-small1-right
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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7 Comments

  • Lillian Parker

    Reply Reply October 8, 2015

    Love the summaries and explanations Alex!! They are a great addition to my science reports. I didn’t know you would need to eat that much chocolate for the same benefits. Choc is so over rated!!

    • Alex

      Reply Reply October 8, 2015

      Thanks, Lillian, music to my ears :-)

  • Jan Bates

    Reply Reply October 8, 2015

    Thanks for the great links. Regarding beans, I have a diabetic friend who enjoys eating beans for the satiety they provide and she dislikes meat, but it raises her blood sugar. Any thoughts on beans and insulin or weight gain?

    • Alex

      Reply Reply October 8, 2015

      Hi Jan – that’s interesting!

      Is your friend familiar with the glycaemic index (GI)? It’s a rating system that captures spikes in blood sugar and insulin after eating a specific amount of a food, compared with eating the same amount of pure glucose.

      Beans and lentils are some of the lowest GI carbs, with a very slow and tiny effect on blood sugar.

      For example, 150 grams of boiled pinto beans have a GI of 14, which means they boost blood sugar only 14% as much as pure glucose. But food with a GI above 95 acts almost like pure glucose.

      You can look up the GI of common foods in this database maintained by the University of Sydney: http://www.glycemicindex.com/foodSearch.php

      You also need to consider how the beans are eaten – blood sugar/insulin spikes could be influenced by the amount consumed (i.e. load) or by other accompanying foods (e.g. sauces) that might raise the compounded GI of a meal.

      But we also know that you can reduce the GI of a meal by adding either protein or fibre. This mix already occurs naturally in beans, that’s why they’re so low GI – even lower than couscous, quinoa and sweet potatoes.

      In relation to weight, several studies suggest that a low GI diet helps promote weight loss, like the first one listed in here :-)

  • Jan Bates

    Reply Reply October 9, 2015

    What a thoughtful response, Alex, complete with a helpful link, thank you! Beans are generally considered a high carbohydrate food and a no-no on low carb diets, but I’ve often wondered if they’ve been unduly villified be a use they are so high in fiber, and your post has given me hope this is true. Your response has me wondering if they could and should be included? Also, can you advise on amounts?

  • Jan Bates

    Reply Reply October 9, 2015

    Still thinking about this Alex…are you saying the low glycemic load is a greater factor than the carbohydrate count being a bit high? I think black beans are about 14 g net carbs (after subtracting the fiber) per 1/2 C, however the fiber content is 8 grams. I would typically think that’s a bit high if trying to keep carbohydrates and insulin lower. It could be done but it would use up a chunk of the day’s allotted carb intake for a diabetic or someone following a ketogenic diet or even trying to maintain their insulin and body fat. Is my thinking incorrect? I want very much to understand the governing principle and truly appreciate your insights!

    Just a PS, it would be wonderful to see an example of what you eat in a day/week…even your whole team!

    • Alex

      Reply Reply October 9, 2015

      My pleasure, Jan. I like your passion and open-minded approach!

      Good questions, let me go one by one. I don’t normally do this – for the benefit of anyone with the same questions I’m happy to make an exception :-)

      BEANS

      Whether to include a new food is a personal choice, so you’d need to consider someone’s preferences, as well as their goals.

      For example, a vegan elite athlete could benefit from their high protein content (beans are one the richest plant-based sources of protein). But if someone is pescatarian, they’re already getting plenty of protein from fish.

      Beans have a relatively high proportion of a starch called “amylose” (up to 40%) compared to other starchy foods. Because amylose is not as digestible as other starches, bean starch is a slow-release carbohydrate. Its digestion takes much longer and it causes a smaller and more gradual rise in blood sugar and insulin than other types of starch, making beans particularly beneficial for people with diabetes.

      If you haven’t tried them before but want to give them a go, you can test your tolerance and whether you like them by combining them with other foods you already eat – e.g. a salad sprinkled with some boiled beans, a chunky vegetable soup with a few lentils, and so on.

      In terms of determining the amounts, per your question, you’d need to consider what nutrients you’re currently focusing on. For example, do you need to meet your daily fibre quota, or your protein quota, are you seeking to mitigate deficiencies in B1, B6, E, K, calcium, iron, magnesium, manganese, molybdenum, choline, etc. etc.?

      CARBS/STARCHES

      Net carbohydrate content in a food (i.e. minus fibre) is not the best determinant of its effect on your blood glucose/insulin. These effects are measured by their glycaemic impact, rather than their sugar/starch content alone.

      Let’s take table sugar as an example. Table sugar is pure glucose and fructose, but did you know that it has a lower GI than bread, potatoes and rice? Really counter-intuitive, right! This doesn’t mean everyone should eat sugar freely, it has a borderline high GI and when mixed with other foods its GI is even higher, plus added sugars bring a host of health issues – more here:

      https://thehealthsciencesacademy.org/science-catch-up/science-catch-up-2/

      https://thehealthsciencesacademy.org/health-tips/added-sugar/

      Low-glycaemic carbohydrates are the kind that won’t spike your blood sugar and insulin. The GI system was actually developed by scientists to help diabetics!

      Hormones, appetite neurochemistry, ketosis, GI, etc. are complex mechanisms with different applications for different individuals – we’ve developed an entire course about them, full curriculum here:

      https://thehealthsciencesacademy.org/cpd-accredited-cyq-endorsed-clinical-weight-loss-certification/

      THE TEAM’S DIETS

      A-ha! I get asked this one a lot. And you’ll be surprised to hear that each one of us in the team eats differently. Different foods, different frequencies, different times, different amounts.

      There isn’t a universal diet that’s great for everyone. Each one of us is so unique, and nutrigenomics (your personal genetics in relation to nutrition) have a lot to do with that.

      For example, Eskimos and Nordics tend to tolerate ketogenic diets better than Mediterraneans; in fact, a large % of Eskimos are allergic to fructose, can you imagine! Most Asians cannot digest lactose because they lack the mutated gene that popped up in Europe about 10,000 years ago. On average saturated fat does not raise heart disease risk, but if you have a genetic disorder called Familial Hypercholesterolemia or a mutation at the APOE gene (epsilon3 and epsilon4 alleles) you would benefit from avoiding it. And so on.

      To make things more complicated, the same person normally experiences biochemical changes within the same year (e.g. stressful periods, environmental changes, food availability, working schedule, physical activity levels, an injury or an illness, sleep, etc.), with the need to adjust things along the way.

      That’s why the team and I are so obsessed with developing client questionnaires and assessments based on scientific findings, to make sure you can personalise your advice as much as possible – and to mitigate the risk of wrong advice. Perhaps our most heavily-loaded course with client assessments in our Advanced Clinical Weight Loss Practitioner (58 client forms).

      One of the best skills you can acquire is to help others figure out what works best for them, nutritionally, on the basis of their current state of health, personal goals, activity levels, food environment, preferences, etc.

      And a good way to achieve that is to think like a scientist: be open to possibilities, test your own hypothesis and experiment. Not everything is set in stone.

      It’s so great to have you on board! Let me know how you get on :-)

      Enjoy your weekend!

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