Ultra Processed Foods & Type 2 Diabetes - What’s the link?

Ultra processed foods (UPFs) have been dominating conversations within the nutrition landscape over the last few months, powered by social media sensations such as Eddie Abbew and by Chris Van Tulleken’s new book Ultra Processed People.

But are they as bad for us as we’re led to believe?

Let’s take a closer look at what we do know about them, some of the nuances that aren’t being discussed and what (if any) link there is between UPFs and type 2 diabetes.

Processing of food happens everywhere. If you’re not eating a completely raw food diet, you are bound to be consuming processed foods. From breads to baked beans to cheese to plant based milks. And it’s not only limited to traditional foods, even common ‘health’ products like protein powders and supplements have been subjected to some level of processing.

So the question is, are they actually harmful to us? And if so, in what amounts?

The main claim against UPFs revolve around its contribution towards obesity but critically evaluating certain foods/nutrients/supplements/diets are notoriously difficult due to the complex nature that is nutrition and health as there are bound to be confounding variables that must be accounted for.

Variables such as the healthy user bias needs to be accounted for. For example, there is a healthy user bias associated with the use of postmenopausal hormone replacement therapy (HRT) and lower incidences of cardiovascular disease. The healthy user bias suggests that because the propensity of individuals who take HRT typically come from higher social economic backgrounds, have better access to good medical care, are less likely to smoke, that these variables needs to be considered.

This means that anything less than well conducted, blinded, randomised controlled trials usually leave us with more questions than answers and in need of more robust evidence.

Other claims commonly made against UPFs include increasing the risk of cardiovascular disease, non-communicable diseases like type 2 diabetes, non-alcoholic fatty liver disease, inflammatory skin conditions and more.

What’s more, with the amount of influence that social media personalities hold in today’s world, the general public are so geared to thinking in such binary terms when it comes to nutrition (thanks Eddie), that we fail to see the ever so important nuances.

Firstly, let’s discuss what we do know.

We know that ultra processed foods feature heavily in a typical ‘standard westernised diet’ today, with studies suggesting this could be as much as half of total energy intake in the U.K (Madruga et al, 2023).

We also know two other important things – that could 100% explain its contribution towards obesity and therefore other metabolic conditions. 

1)    They are very, very easy to overeat on.

 20 weight-stable adults who were split into 2 groups and were told to either eat a minimally processed diet or ultra processed diet for 2 weeks proved this matter of fact point. The adults were kept in metabolic wards over this period which excluded any external/environmental factors that could influence their hunger or eating desires (Hall et al, 2019).

The meals that both groups were provided contained the same number of calories, macros, sugar, sodium and fibre but were told to eat as much or as little as desired.

The results were unanimous and clear for everybody to see. While on the ultra processed diet, subjects tended to consume an extra 500 calories a day, coming from mainly carbs and fats, not so much from the protein.

Now this doesn’t require a PhD in human nutrition to have predicted this outcome but here are the possible mechanisms behind it.

-       UPFs like white bread, cakes/biscuits and cereals usually contain little to no fibre. Fibre is not only critical for the health of our gut microbiome but is incredibly satiating (Salleh et al, 2019).

-       People tend to eat faster when eating UPFs and therefore the delayed time to register satiation can lead to an overall increased consumption of calories (2).

2)    They seem to produce a considerably lower thermic response than their whole food counterparts

 We burn calories when we digest foods. About 10% of our total daily calories burned comes through this process. It’s called the thermic effect of food. It’s not a huge amount, but it’s still something.

And when you consider that you don’t even need to lift a finger to burn these calories, (ok you’ll need to lift your fork up to your mouth, but that’s about it) it’s essentially calories burned for FREE (and therefore supporting weight management).

The catch? Different macronutrients provide different levels of thermogenesis (the heat produced by the body when it digests food).

Here’s how many calories your body would burn if you ate 100 calories of the 3 macronutrients

Fats – 0-4% - resulting in a net calorie intake of 96-100 kcal

Carbs – 5-15% - resulting in a net calorie intake of 85-95 kcal

Protein - 20-30% - resulting in a net calorie intake of 70-80 kcal

As you can see, protein has the highest thermic effect of food (hence meat sweats) and increasing protein intake for weight loss or long-term weight maintenance can actually become a very important nutritional strategy.

Along with this, It’s widely accepted now that fibre plays a role in this whole story too. It turns out that some people can extract either more or less calories from the foods that they eat, based on their gut microbiome and the degree of processing of the food.

For example, this study of 18 healthy adults who consumed a 28g serving of almonds a day for 2 weeks showed that on average they absorbed about 128 calories from the nuts compared to the stated 168-170 kcal on standard food labels. Some of the calories wrapped up in the fibrous content of foods actually go through the digestive tract unmetabolized. Again, another source of ‘free calories’ supporting weight management (Holscher et al, 2018).

The problem with UPFs is that they tend to have a really low thermic of food. They are usually low in both protein and fibre. Hence why it’s so easy to overconsume, there is literally nothing in them that is activating our satiety signals.

Ok so what about the things that we don’t know about UPFs?

The most logical question here is, in the scenario where UPFs are consumed in the absence of a calorie surplus and any weight gain, is there actually any evidence suggesting that they are harmful to us?

Now you don’t have to scroll on social media for longer than 10 seconds to find an ‘influencer’ reeling of all the ‘chemicals’ from the back of a crisp packet, like flavourings, artificial sweeteners, E-numbers, suggesting that it’s not ‘real’ food. But remember that these are usually found in UPFs in relatively small amounts.

It would be handy to have a set of healthy identical twins both eating maintenance calories (and therefore no weight gain), one twin consuming just whole foods, whilst the other consumes exclusively UPFs and monitor their health over time. I propose that the lack of fibre in the UPF diet may have residual consequences, whether that be constipation or a change in the composition of the gut microflora which could lead to other unfavourable health impacts.

I believe at this point though, as cliché as it sounds, it really is everything in moderation. It’s highly unlikely that people with overweight/obesity got there by having the odd slice of white toast with their eggs in the morning.

And what about for type 2 diabetics?

The progression of type 2 diabetes is fuelled by the build up and presence of intra-hepatic and intra-muscular fat (fat inside the liver and skeletal muscle), also commonly known as visceral fat (Dhokte & Czaja, 2024). This effectively shuts down the normal functioning of insulin to bring glucose out of the blood and into the cells of the muscle and liver. And the number #1 cause of visceral fat build up? Weight gain.

So the only real and viable connection between UPFs and type 2 diabetes is a simple one, but it’s an enormously potent one.

Eating too many UPFs makes it easier to gain weight and visceral fat, which greatly increases the risk of type 2 diabetes.

Not only that, this weight gain could also lead to other metabolic complications such as high blood pressure, high triglycerides and high cholesterol. All of which can contribute towards atherosclerosis and heart attacks.

The DIRECT study has shown that remission of type 2 diabetes is possible with about 15kg of weight loss (diabetes.org.uk) and if there’s one thing I know about successful weight loss stories having worked with hundreds of clients over the last 12 years – it’s that protein and fibre consumption matters a lot.

Aiming for about 20-25g of fibre for females and about 25-35g for males is a healthy target and a protein intake of 1.8-2.4g per kilo of lean mass weight is also ideal.

It’s clear that UPF consumption has been on the rise as well as the cases of obesity and type 2 diabetes. Outside of the strong possibility for UPFs to cause weight gain, I don’t think they are as harmful as they’ve been made out to be. Especially when you consider that non-nutritive sweetened beverages (diet drinks) performed better than water in a 52-week weight management program (Harold et al, 2024), if they can be consumed as part of a balanced diet to maintain weight or even to help facilitate weight loss – you would have to say that it’s a net positive.

Having said that, there are many factors to consider when dealing with weight loss and healthy eating advice - socioeconomic backgrounds, education level, having the available time to cook, mental health conditions and more. I get that it’s not as simple as just waving a magic wand and magically producing the ‘perfect’ balanced diet, but hopefully this article has helped provide some context and perspective towards UPFs in a more critical manner.

References

https://www.diabetes.org.uk/about-us/news-and-views/weight-loss-can-put-type-2-diabetes-remission-least-five-years-reveal-latest-findings

Dhokte S, Czaja K. Visceral Adipose Tissue: The Hidden Culprit for Type 2 Diabetes. Nutrients. 2024 Mar 30;16(7):1015. doi: 10.3390/nu16071015. PMID: 38613048; PMCID: PMC11013274.

Hall KD, Ayuketah A, Brychta R, Cai H, Cassimatis T, Chen KY, Chung ST, Costa E, Courville A, Darcey V, Fletcher LA, Forde CG, Gharib AM, Guo J, Howard R, Joseph PV, McGehee S, Ouwerkerk R, Raisinger K, Rozga I, Stagliano M, Walter M, Walter PJ, Yang S, Zhou M. Ultra-Processed Diets Cause Excess Calorie Intake and Weight Gain: An Inpatient Randomized Controlled Trial of Ad Libitum Food Intake. Cell Metab. 2019 Jul 2;30(1):67-77.e3. doi: 10.1016/j.cmet.2019.05.008. Epub 2019 May 16. Erratum in: Cell Metab. 2019 Jul 2;30(1):226. Erratum in: Cell Metab. 2020 Oct 6;32(4):690. PMID: 31105044; PMCID: PMC7946062.

Harrold JA, Hill S, Radu C, Thomas P, Thorp P, Hardman CA, Christiansen P, Halford JCG. Non-nutritive sweetened beverages versus water after a 52-week weight management programme: a randomised controlled trial. Int J Obes (Lond). 2024 Jan;48(1):83-93. doi: 10.1038/s41366-023-01393-3. Epub 2023 Oct 5. PMID: 37794246; PMCID: PMC10746539.

Holscher HD, Taylor AM, Swanson KS, Novotny JA, Baer DJ. Almond Consumption and Processing Affects the Composition of the Gastrointestinal Microbiota of Healthy Adult Men and Women: A Randomized Controlled Trial. Nutrients. 2018 Jan 26;10(2):126. doi: 10.3390/nu10020126. PMID: 29373513; PMCID: PMC5852702.

Madruga M, Martínez Steele E, Reynolds C, Levy RB, Rauber F. Trends in food consumption according to the degree of food processing among the UK population over 11 years. Br J Nutr. 2023 Aug 14;130(3):476-483. doi: 10.1017/S0007114522003361. Epub 2022 Oct 19. PMID: 36259459.

Salleh SN, Fairus AAH, Zahary MN, Bhaskar Raj N, Mhd Jalil AM. Unravelling the Effects of Soluble Dietary Fibre Supplementation on Energy Intake and Perceived Satiety in Healthy Adults: Evidence from Systematic Review and Meta-Analysis of Randomised-Controlled Trials. Foods. 2019 Jan 6;8(1):15. doi: 10.3390/foods8010015. PMID: 30621363; PMCID: PMC6352252.