A claim you hear on longevity podcasts

Does sugar cause type 2 diabetes?

The claim checked: Sugar, refined starches, grains and ultra-processed food cause type 2 diabetes Hear it at 0:44

What do the studies say?

Leaning for

All ten studies found a partial link: sugary drinks and high-glycemic diets raised diabetes risk, but so did red and processed meat, and the effects were modest.

Computed from 10 studies that test this point, each judged by two readers, in full. 10 more studies are waiting for a full read and do not count yet.

What was said on the podcast?

“lean red meat doesn't contain sugar it's not a plausible link to diabetes and it's sugar and refined starches and Grains and Ultra processed food that cause diabetes”

Mark Hyman, The Dr. Hyman Show · Debunking The Link Between Red Meat & Type 2 Diabetes (Avoid This Food Instead) | Dr. Mark Hyman · 0:44 on YouTube
Comes up in 41 episodes of the show.

Point 1 of 2 Leaning for

Sugar and refined carbohydrates are the primary cause of type 2 diabetes

Agree 0

None.

Partly agree 10

pooled analysis · 2017 · landmark

“In high versus low and linear dose–response meta-analysis, a link with T2D risk was identified for 6 out of the 12 food groups; for the consumption of whole grains, dairy, and fruits this association was inverse; for processed meat, red meat, and SSB consumption, the association was positive.”

Food groups and risk of type 2 diabetes mellitus: a systematic review and meta-analysis of prospective studies. Eur J Epidemiol
Who: adults (18+) free of type 2 diabetes at baseline in prospective cohort studies from Europe, America, Asia and Australia
PMID 28397016

pooled analysis · 2019 · landmark

“The quality of evidence was graded as high only for whole grain, cereal fibre, and moderate consumption of total alcohol, which decreased the incidence for type 2 diabetes; and for red meat, processed meat, bacon, and sugar sweetened beverages, which increased the incidence for the disease.”

Role of diet in type 2 diabetes incidence: umbrella review of meta-analyses of prospective observational studies. BMJ
Who: adults in prospective cohort studies pooled in published meta-analyses of diet and incident type 2 diabetes
PMID 31270064

pooled analysis · 2019 · landmark

“Critical analyses of prospective cohort studies provide robust evidence that diets higher in glycemic index (GI) and load (GL), independently of dietary fiber, substantially elevate the risk of type-2 diabetes among healthy populations of men and women, each sufficiently meeting the criteria of importance to public health nutrition.”

Dietary Glycemic Index and Load and the Risk of Type 2 Diabetes: A Systematic Review and Updated Meta-Analyses of Prospective Cohort Studies. Nutrients
Who: Healthy adults free of T2D at baseline in prospective cohort studies from the USA, Europe, Asia and Australia
PMID 31195724

Show 7 more Show fewer

other primary study · 2013

“The dietary GI was significantly associated with the risk of diabetes among women in the analysis adjusted for age and study area, but the association was attenuated and no longer significant after additional adjustments for multiple factors.”

Dietary glycemic index, glycemic load and incidence of type 2 diabetes in Japanese men and women: the Japan Public Health Center-based Prospective Study. Nutr J
Who: 27,769 men and 36,864 women aged 45-75 in the Japan Public Health Center-based Prospective Study
PMID 24370346

systematic review · 2025

“In contrast, high intakes of sugar-sweetened beverages and red and processed meats are associated with an increased risk of type 2 diabetes and metabolic syndrome.”

Umbrella Review of Systematic Reviews and Meta-Analyses on Consumption of Different Food Groups and Risk of Type 2 Diabetes Mellitus and Metabolic Syndrome. J Nutr
Who: meta-analyses of prospective cohort studies in adults on food-group intake and incident type 2 diabetes, metabolic syndrome and diabetes mortality
PMID 40122387

pooled analysis · 2010 · landmark

“For type 2 diabetes, based on data from eight prospective cohort studies (nine data points), including 310,819 participants and 15,043 cases of type 2 diabetes, participants in the highest category of SSB intake had a 26% greater risk of developing type 2 diabetes than participants in the lowest category of intake.”

Sugar-sweetened beverages and risk of metabolic syndrome and type 2 diabetes: a meta-analysis. Diabetes Care
Who: adults in prospective cohorts from the U.S., Finland and Singapore (predominantly white, black and Chinese)
PMID 20693348

pooled analysis · 2015 · landmark

“Additionally, the average population attributable fraction of no more than 20% confirms the importance of modifying multiple lifestyle risk factors rather than a single dietary component, for the primary prevention of type 2 diabetes.”

Consumption of sugar sweetened beverages, artificially sweetened beverages, and fruit juice and incidence of type 2 diabetes: systematic review, meta-analysis, and estimation of population attributable fraction. BMJ
Who: Diabetes-free adults 18+ in 17 prospective cohorts (US, Europe, Japan, Singapore)
PMID 26199070

pooled analysis · 2018 · landmark

“Even though more than one third of the associations examined various dietary factors, only six of them showed convincing or highly suggestive relationship with T2DM and the demonstrated effect sizes were modest.”

Risk factors for type 2 diabetes mellitus: An exposure-wide umbrella review of meta-analyses. PLoS One
Who: umbrella review of meta-analyses of observational studies on non-genetic risk factors for type 2 diabetes in adults
PMID 29558518

pooled analysis · 2012 · landmark

“Overall, the random effects model summarising all seven comparisons suggested a positive association; the pooled relative risk was 1.27 (95% confidence interval 1.04 to 1.54), although significant heterogeneity was detected (I 2 =72.2%; Cochrane Q test P=0.001).”

White rice consumption and risk of type 2 diabetes: meta-analysis and systematic review. BMJ
Who: Adults free of diabetes at baseline in 4 prospective cohorts (China, Japan, US, Australia), aged 26-87
PMID 22422870

pooled analysis · 2014

“The included studies were observational, so their results should be interpreted cautiously, but findings indicate a positive association between sugar-sweetened soft drink intake and type 2 diabetes risk, attenuated by adjustment for BMI.”

Association between sugar-sweetened and artificially sweetened soft drinks and type 2 diabetes: systematic review and dose-response meta-analysis of prospective studies. Br J Nutr
Who: adults in 9 prospective cohorts (US, Europe, Asia) recruited from generally healthy populations
PMID 24932880

Disagree 0

None.

Point 2 of 2 Leaning for

Insulin resistance, the root cause of type 2 diabetes, comes from a diet high in sugar, refined flour, grains and ultra-processed food, and from inactivity and low muscle

Two of ten studies backed it and seven partly did: bed rest cut insulin sensitivity, by 29% in one. Most sugar trials found no rise in insulin resistance at usual intakes.

Computed from 10 studies that test this point, each judged by two readers, in full. 4 more studies are waiting for a full read and do not count yet.

Agree 2

other primary study · 2016 · landmark

“Bed rest induced a 29 ± 5% decrease in whole-body insulin sensitivity (P < 0.01).”

One Week of Bed Rest Leads to Substantial Muscle Atrophy and Induces Whole-Body Insulin Resistance in the Absence of Skeletal Muscle Lipid Accumulation. Diabetes
Who: 10 healthy young men (age 23, BMI 23) without type 2 diabetes
PMID 27358494

controlled trial · 2014

“In the presented study we induced impaired glucose tolerance in metabolically healthy, sedentary young male subjects without any first degree relatives being diabetic during experimental bed rest.”

How fast is recovery of impaired glucose tolerance after 21-day bed rest (NUC study) in healthy adults? ScientificWorldJournal
Who: Metabolically healthy, sedentary young men (mean age 27.6) with no first-degree diabetic relatives
PMID 24741361

Partly agree 7

pooled analysis · 2018

“Conclusion The effects of food sources of fructose-containing sugars on glycaemic control appear to be both energy and food source dependent.”

Food sources of fructose-containing sugars and glycaemic control: systematic review and meta-analysis of controlled intervention studies. BMJ
Who: people with and without diabetes in controlled feeding trials of food sources of fructose-containing sugars (substitution, addition, subtraction, ad libitum designs)
PMID 30463844

pooled analysis · 2016

“The data do not support meaningful effects of short-term isocaloric or hypercaloric fructose on fasting insulin concentrations, HOMA-IR, or peripheral or muscle insulin sensitivity.”

Effect of fructose consumption on insulin sensitivity in nondiabetic subjects: a systematic review and meta-analysis of diet-intervention trials. Am J Clin Nutr
Who: 1005 normal-weight and overweight/obese nondiabetic adults in controlled diet-intervention trials
PMID 27935520

controlled trial · 2017

“We show for the first time that 21 days of bed rest reduced skeletal muscle mitochondrial respiration concomitant with decreased insulin sensitivity, metabolic rate and fat-free mass.”

Bed rest and resistive vibration exercise unveil novel links between skeletal muscle mitochondrial function and insulin resistance. Diabetologia
Who: healthy young men in a European Space Agency head-down-tilt bed rest crossover study
PMID 28500394

Show 4 more Show fewer

controlled trial · 2018

“The absence of clear evidence of whole-body glucose intolerance and insulin resistance was surprising.”

Metabolic Inflexibility Is an Early Marker of Bed-Rest-Induced Glucose Intolerance Even When Fat Mass Is Stable. J Clin Endocrinol Metab
Who: 10 healthy, active men (BMI 20-25, mean age 31) in a crossover 21-day bed-rest study; 9 completed both arms
PMID 29546280

other primary study · 2015

“Collectively, our results suggest that acute inactivity leads to deleterious impairments in insulin sensitivity and glycemic control, but that these changes are not due to postprandial blood flow impairments.”

Acute inactivity impairs glycemic control but not blood flow to glucose ingestion. Med Sci Sports Exerc
Who: 14 healthy, recreationally active young men (24±1.1 yrs)
PMID 25207931

trial or observed group · 2023

“The results of the present longitudinal study suggest that loss of lower limb muscle mass is a risk factor for development of insulin resistance independent of obesity in nondiabetic older Japanese adults although such a role of risk factor is not shared by upper limb muscle mass, trunk muscle mass, muscle strength, or muscle function.”

Preserved Lower Limb Muscle Mass Prevents Insulin Resistance Development in Nondiabetic Older Adults. J Am Med Dir Assoc
Who: 194 community-dwelling nondiabetic Japanese adults aged >=65 without insulin resistance at baseline (Tanno-Sobetsu study)
PMID 36592939

controlled trial · 2019

“In conclusion, we show that in healthy subjects, metabolic deterioration with inactivity only manifests in the setting of energy surplus.”

Metabolic Implications of Diet and Energy Intake during Physical Inactivity. Med Sci Sports Exerc
Who: 10 healthy, physically active young adults (6 men, 4 women), aged 24 ± 1 years, BMI < 28
PMID 30694977

Disagree 1

controlled trial · 2015

“In conclusion, findings from this randomized controlled trial suggest that fructose containing sugars consumed at the 50th percentile population consumption level do not increase insulin resistance or decrease glucose tolerance.”

No Effect of Added Sugar Consumed at Median American Intake Level on Glucose Tolerance or Insulin Resistance. Nutrients
Who: Normoglycemic, weight-stable non-smoking men and women aged 20-60 with BMI 21-35
PMID 26512691

What else was said but not tested?

Red meat is not a plausible cause of type 2 diabetes ('it's BS')
Cutting ultra-processed food, refined grains, sweets and especially sugar-sweetened beverages improves insulin sensitivity

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