Carbohydrate quality and weight

by | Oct 8, 2023 | Nutrition

An article from NBC News says sugar should be behind bars and starchy vegetables are an even bigger enemy. The same week a video came out from popular fitness trainer Jordan Syatt, who ate candy, bread, pumpkin lattes, even pure sugar for 30 days and lost 6kg (12lbs)

Is sugar really that bad? Are potatoes even worse than refined sugar? What do you make of this?

We’ll look first at an article and study on the quality of carbohydrates and their effect on body weight and what other studies have to say about it.

NBC news released an article about a study (Wan Y, 2023) where the authors analyzed the diets of 137,000 people over the course of more than 20 years!
They found less weight gain in people who ate more whole grains, fruits and non-starchy vegetables – like broccoli, carrots and spinach – and less refined grains, starchy vegetables and sweetened beverages.

Here is how every 100g/day resulted in weight change over 4 years:

🥤added sugar +0.9kg (2-3 cans of sweetened beverages per day)

🌽 starchy vegetables +1.5kg

🥔sugars from processed starchy vegetables (mainly potatoes) +2.6kg

🍞 processed cereals +0.8kg

fibre -0.8kg (for every 10g)

🍞 Wholegrain cereals -0.4kg

🍉 Fruits -1.6kg

Non-starchy vegetables -3kg

One of the study authors even said: “Is sugar the villain? It should be behind bars, but interestingly, there are bigger villains. Overall, starch is a bigger villain.”
Starchy foods include white bread and vegetables, such as peas, corn and potatoes.
They reasoned that starchy vegetables result in a higher rise in blood sugar (and insulin) and this results in overeating and higher amounts of fat storage. In the article on blood sugar, I described that elevated blood sugar does not always result in overeating or weight gain.

Starchy vegetables are worse than sugar for weight maintenance?!

Starchy foods include white bread, peas, corn and potatoes, but also lentils and beans.

We can tell from other studies that starchy vegetables, especially legumes but also potatoes, do not cause weight gain, they even help with weight loss. (Aune D et al.))

An analysis of 21 studies found that people who ate legumes lost more weight on average than those who did not eat legumes (Vujicic I et al.)
Cooked potatoes do not appear to be a food that has an association with weight gain. Of the common foods, they have the highest effect on satiety.

Why do we see the opposite claim here? The catch is in the details.

In the study cited in the NBC article, they lumped sweet potatoes, boiled potatoes, baked potatoes, corn, peas, even French fries and potato chips into the group of starchy vegetables.

According to the U.S. Department of Agriculture’s (USDA) Economic Research Service, these are the most consumed starchy vegetable among American adults:

  • Potatoes: 22.4 kilograms per person per year
  • Tomatoes: 14.1 kilograms per person per year
  • Corn: 11.1 kilograms per person per year

American adults often consume these foods in processed forms, such as French fries, pizza sauce, and cornbread. Processed starchy vegetables tend to be high in calories, sodium and unhealthy fats. French fries and potato chips encourage overeating.

What does Cochrane say?

What is Cochrane?

Cochrane is a global independent network of researchers, professionals, patients, carers and individuals interested in health. They are involved in producing systematic reviews of primary research to provide evidence for healthcare decision-making. This organization synthesizes research findings in the field of medicine and produces evidence-based decisions for health care, engaging health professionals, patients, and policy makers. Cochrane is recognized for its commitment to high-quality information that informs better health decisions

According to Cochrane research released in June 2023 [7], “Diets with a low glycemic index or glycemic load are likely to lead to little or no difference in weight change. The results suggested that a low glycemic index or glycemic load diet may improve mood, but the actual effect is likely to be substantially different from the effect estimate.”

Jordan Syatt lost 6kg in 30 days by eating sugar-rich foods

Trainer and fitness influencer Jordan Syatt has decided to eat foods that will raise his blood sugar for 30 days and lose weight at the same time. In doing so, he wanted to experimentally show that neither elevated insulin nor blood sugar hinder weight loss and thereby disprove the typical preconceptions associated with carbohydrates and especially sugars:

  1. Insulin is the reason why we gain weight or prevents weight loss. This is why calories “don’t work”
  2. Sweet foods cause hunger
  3. Sugar is a poison / makes you unhealthy
“I’m making this video and taking it to the extreme to make a point that you can be spiking your blood sugar and lose weight.”

During the experiment, he consumed a variety of foods, including white bread, gummy candies, pumpkin lattes, potatoes, oatmeal, and even a quarter cup of pure refined sugar.

Here are his key observations:

  • Fast carbohydrates (those with a high glycemic index) are said to cause a spike and subsequent drop in blood sugar. This causes fatigue and hunger. In some cases this is true, but not always. For example, after 4 slices of white bread, his sugar dropped 33 units without him experiencing hunger or a drop in energy. Similarly, after potatoes (80g carbs) his sugar went from 79 to 143! (Normally we don’t want to see an increase of more than 30 units). He felt great!
  • After eating about 60g of pure sugar he felt super energetic at first, but after 2 hours there was a decline and for the next 2-3 hours he felt exhausted.
  • The pumpkin spice latte (65g sugar) didn’t have much effect on his blood sugar. Probably due to the fact that it also contained fat and protein as opposed to pure sugar. It was basically like a meal replacement. He remarked, “It’s like I’m eating cheesecake in the form of a drink. I can’t even enjoy it, it’s too sweet. It’s great, but I don’t want to have it every day. I can’t believe people drink it every day. I’m not surprised they don’t want to eat fruit afterwards.”
  • Healthy people nowadays pay a lot of attention to blood sugar and try to keep it in check. But judging foods only by how they affect blood sugar is not helpful. Oatmeal raised Jordan’s blood sugar more than gummy candy. That doesn’t mean gummy candies are healthier.
  • You can lose weight even with high blood sugar. Jordan lost about 12 pounds (6kg)  in 30 days. But apart from the foods mentioned above, he also ate a varied, nutritious diet.
  • His blood tests after the experiment showed an improvement in HDL cholesterol levels (probably due to weight loss), but his blood sugar and HbA1C levels were unchanged.


Based on studies, we can say that the quality of carbohydrates plays a role in energy intake. Ultimately, though, it’s about the balance between calories in and calories out. However, it is easier to regulate energy intake if we eat balanced meals consisting mainly of whole grains, fruits and legumes rather than industrially processed foods.

Processed foods, including starchy vegetables in the form of chips, crisps and sauces with added fats and sugars, can lead to weight gain, so it is a good idea to be aware of the impact on the individual – for some it is neutral and for others it can lead to overeating. The dose makes all the difference.

WHO recommends reducing intake of added sugars to less than 10% of total energy.

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  1. Wan YTobias D KDennis K KGuasch-Ferré MSun QRimm E B et al. Association between changes in carbohydrate intake and long term weight changes: prospective cohort study doi:10.1136/bmj-2022-073939
  2. Vujicic I et al. The effects of legume consumption on body weight and body composition: A systematic review and meta-analysis of randomized controlled trials. Nutrients. 2016 Sep 14;8(9):569.
  3. Aune D et al. Whole grain and legume consumption and changes in body weight and composition in the Iowa Women’s Health Study. Am J Clin Nutr. 2011 Oct;94(4):1165-71.
  4. Potatoes and risk of chronic disease: a systematic review and dose–response meta-analysis
  5. Potatoes and tomatoes are the most commonly consumed vegetables: USDA Economic Research Service, Food Availability and Consumption Data, available at…
  6. 50.3% of American adults consumed starchy vegetables on a given day: Centers for Disease Control and Prevention, Fruit and Vegetable Consumption Among Adults in the United States, 2015-2018, available at
  7. Chekima K, Yan SW, Lee SWen Huey, Wong TZe, Noor MI, Ooi YBH, Metzendorf M-I, Lai NM. Low glycaemic index or low glycaemic load diets for people with overweight or obesity. Cochrane Database of Systematic Reviews 2023, Issue 6. Art. No.: CD005105. DOI: 10.1002/14651858.CD005105.pub3. Accessed 22 October 2023.