Weekend Read · Week 7 · 11 min read · Reviewed against peer-reviewed evidence, October 2026
The short version
The habits you've built over seven weeks matter beyond how you feel this month. Several of them overlap with the things researchers link to brain health later in life. In 2024, a major international report listed 14 risk factors for dementia that can be changed, including diabetes, physical inactivity and high blood pressure. It estimated that tackling them could prevent or delay nearly half of dementia cases across whole populations. That's a population figure, not a promise to any one person.
Food is part of that picture, but the evidence is more mixed than wellness headlines suggest. The honest case for keeping going is this: real food, steady blood sugar, daily movement and decent sleep are linked with better brain health later, and many people notice they think more clearly now.
The question underneath "Why keep going?"
By Week 7, the cravings have usually quietened and berries are back. So it's fair to ask what the long game is.
For many women in midlife, the real question sits underneath. Am I ageing well? Is this fog my hormones? Will I end up like my mum or dad? This article looks at what the research says about brain health, how strong it is, and where your habits fit. It isn't about fear. Most of what's good for your brain at 75 also helps you think clearly at 3pm on a Tuesday.
Nearly half of dementia cases are linked to risk factors that can change
The Lancet Commission on dementia prevention, intervention and care brings together leading researchers to review the evidence every few years. Its 2024 report named 14 modifiable risk factors spread across life: less education in early life; hearing loss, high LDL cholesterol, depression, traumatic brain injury, physical inactivity, diabetes, smoking, high blood pressure, obesity and excess alcohol in midlife; and social isolation, air pollution and untreated vision loss in later life (Livingston et al., 2024).
The Commission estimated that addressing these factors could prevent or delay nearly half of dementia cases. The authors add two caveats. It's a population estimate, not a guarantee for any one person. And some of these links may be only partly causal.
Still, it's a hopeful finding. Several are things this program already touches: blood sugar, movement and blood pressure.
Blood sugar and the brain are closely linked
Diabetes is one of the 14, and one of the most studied. A meta-analysis of 28 prospective studies found that people with diabetes had a 73% higher risk of developing dementia of any type than people without it. The risk of vascular dementia, the kind linked to blood vessel damage, was more than double (Gudala et al., 2013).
These are observational studies, so they can't prove diabetes causes dementia. People with diabetes often have other risk factors too, such as high blood pressure. But the link has held up across many studies, and it's one reason diabetes is on the Commission's list.
What "type 3 diabetes" means, and doesn't
You may have seen Alzheimer's disease called "type 3 diabetes" online. The phrase comes from a research hypothesis. Some scientists argue that Alzheimer's involves problems with how the brain responds to insulin and uses glucose for fuel, and that these overlap with what happens in type 1 and type 2 diabetes (de la Monte, 2014).
It's an interesting idea that's still being tested. It isn't a diagnosis or an official disease category, and it doesn't mean eating sugar gives you Alzheimer's. It does underline what the diabetes research suggests: metabolic health and brain health seem to be connected.
The MIND diet trial is the most useful "disappointing" result in nutrition
If you've read about food and brain health, you've probably met the MIND diet. It's a blend of the Mediterranean diet and the DASH diet (designed to lower blood pressure), tweaked to include foods that earlier studies had linked with lower dementia risk.
The early evidence looked striking. In a 2015 study of 960 older adults, people whose diets most closely matched the MIND pattern had slower cognitive decline. The gap between the highest and lowest scorers was equivalent to being 7.5 years younger (Morris et al., 2015). But it was observational, and the authors said so themselves: a trial was needed.
That trial was published in 2023. Researchers randomly assigned 604 older adults with a family history of dementia to the MIND diet or a control diet for three years. Both groups got the same support. At the end, both groups' thinking scores had improved, and the difference between them was small and not statistically significant. MRI brain scans were similar too (Barnes et al., 2023).
So what does that mean?
It doesn't mean food doesn't matter. Both groups changed how they ate, and both improved. The trial couldn't show that the specific MIND foods beat a general healthier-eating plan over three years, in people without memory problems. Three years may also be short for something that develops over decades.
The fair reading: there's no single brain diet to buy into. A broad pattern of real food, plenty of plants and less ultra-processed food is the sensible bet, and it's the one you've been making for seven weeks.
Ultra-processed food is linked with faster cognitive decline
A large Brazilian study followed 10,775 adults aged 35 to 74 for a median of eight years. People who got a larger share of their daily energy from ultra-processed foods (everyone above the lowest quarter) showed a 28% faster rate of decline in overall thinking scores, and a 25% faster decline in executive function, the skills you use to plan and juggle tasks (Gomes Gonçalves et al., 2023).
Again, this is observational, and it's one study. People who eat a lot of ultra-processed food may differ in other ways the researchers couldn't fully adjust for. But the habit it points to is a practical one: cook a little more from scratch.
That's exactly what Week 7 asks.
Your gut talks to your brain, and the vagus nerve carries part of the message
The gut and brain are in constant two-way contact. Researchers call it the microbiota–gut–brain axis. Messages travel through the immune system, through compounds your gut bacteria make when they ferment fibre, called short-chain fatty acids, and along the vagus nerve, a long nerve running from the brainstem to the gut (Cryan et al., 2019).
Much of the strongest evidence still comes from animal studies, so treat this as a promising reason to keep eating fibre and fermented foods, not proof that a probiotic will sharpen your memory. If you want more on how the vagus nerve, stress and blood sugar interact, our article on the cortisol and blood sugar loop goes deeper.
Movement might be the most underrated brain habit
Physical inactivity is on the Commission's list, and the evidence here includes randomised trials. In one, 120 older adults were randomly assigned to aerobic exercise training or to a control group. In the exercise group, the hippocampus, a brain region central to memory, grew by about 2%. That roughly reversed one to two years of age-related shrinkage, and memory improved with it. In the control group, it kept shrinking (Erickson et al., 2011).
A 2025 review of step-count studies found that, compared with 2,000 steps a day, around 7,000 was linked with a 38% lower risk of dementia (Ding et al., 2025). That estimate came from only two studies and is observational, but it suggests you don't need 10,000 steps for movement to count.
Your 20-minute daily movement plan is one of the habits most worth keeping.
The evidence map
A snapshot of the studies behind this article. "Strong" means a systematic review or meta-analysis with a consistent result. "Moderate" means good-quality individual studies. "Emerging" means early or small studies, or mostly animal research.
| Theme | Study | Strength | Finding |
|---|---|---|---|
| Modifiable risk | Livingston et al., 2024 | Strong | 14 modifiable risk factors; tackling them could prevent or delay nearly half of cases across populations. |
| Diabetes and dementia | Gudala et al., 2013 | Strong | 28 observational studies: diabetes linked with 73% higher risk of dementia. |
| "Type 3 diabetes" | de la Monte, 2014 | Emerging | A hypothesis that Alzheimer's involves brain insulin resistance. Not a diagnosis. |
| MIND diet (observational) | Morris et al., 2015 | Moderate | Higher MIND scores linked with slower cognitive decline in 960 older adults. |
| MIND diet (trial) | Barnes et al., 2023 | Moderate | Randomised trial, 604 people, 3 years: both groups improved; no significant difference. |
| Ultra-processed food | Gomes Gonçalves et al., 2023 | Moderate | Higher intake linked with 28% faster global cognitive decline over about 8 years. |
| Gut–brain axis | Cryan et al., 2019 | Emerging | Two-way gut–brain signalling, including via the vagus nerve; much evidence is from animals. |
| Exercise and memory | Erickson et al., 2011 | Moderate | Aerobic training grew the hippocampus by about 2% and improved memory in older adults. |
| Daily steps | Ding et al., 2025 | Moderate | About 7,000 steps a day linked with 38% lower dementia risk vs 2,000 (two studies). |
| Menopause and thinking | Greendale et al., 2009 | Moderate | Learning dipped in perimenopause and rebounded after menopause. |
| Menopause and sleep | Kravitz et al., 2008 | Moderate | Trouble falling and staying asleep increased through the menopause transition. |
This week: swap one packaged food for homemade
Week 7's food rules are the same as Week 6. One or two serves a day of low-fructose fruit such as berries, kiwi or citrus, and a little rice malt syrup or stevia if you want it. Added sugar, honey and syrups stay out. The new habit is small on purpose: pick one packaged food you buy every week and make it yourself instead.
One swap doesn't change your brain. The point is the skill. Each thing you learn to make is one less ultra-processed food in your week for good, and that's how the program keeps working after Week 8.
1. Choose something you buy on autopilot
Muesli bars, granola, crackers, salad dressing, pasta sauce, stock or dips. Whichever you go through fastest is your swap.
2. Make it part of your Sunday cook-up
A jar of olive oil and lemon dressing or a tray of nut-and-seed crackers takes little extra time when you're already in the kitchen. Make enough for the week.
3. Feed your gut while you're at it
Homemade swaps are an easy place to add fibre. Plain Greek yoghurt with berries instead of a flavoured tub, or a dip made from white beans.
4. Keep the 20 minutes
Your movement plan has some of the clearest brain evidence behind it. A brisk walk after dinner counts.
If you're in perimenopause or menopause
Brain fog in midlife is real, and it's measurable. In the Study of Women's Health Across the Nation (SWAN), researchers tested more than 2,300 women over four years. Normally people do a little better each time they repeat a memory test, because they learn. During perimenopause, that improvement stalled. After menopause, it came back to premenopausal levels (Greendale et al., 2009). The authors concluded the difficulties may be time-limited.
That's reassuring. Losing words mid-sentence in your late forties is common, and the SWAN findings suggest it's often a phase rather than a lasting change.
Sleep is part of the story. In SWAN, trouble falling asleep and staying asleep became more common as women moved through the transition, and was linked with more hot flushes and with falling oestrogen (Kravitz et al., 2008). Poor sleep alone can make thinking feel slower. Less alcohol and daily movement may help, and so can talking to your GP about night sweats and hot flushes if they're breaking your sleep. If brain fog is severe or getting worse, see your GP. Thyroid problems, low iron, depression and sleep apnoea are all worth ruling out.
What this article isn't saying
- That eating well will prevent dementia. No diet has been shown to do that. These are risk factors, and changing them shifts odds, not destiny.
- That people who develop dementia did something wrong. Age and genes are the biggest risk factors, and neither can be changed.
- That sugar causes Alzheimer's. The research is about long-term metabolic health, not a slice of birthday cake.
- That you need a special brain supplement or probiotic. The evidence doesn't support buying one for this reason.
Common questions
Dementia runs in my family. Is there any point?
Yes. Family history raises risk, but the 14 factors apply to everyone, and many also affect your heart, mood and energy now. If you're worried, ask your GP about your blood pressure, cholesterol and hearing.
If the MIND diet trial found no difference, why bother?
Because both groups improved, and both had changed how they ate. The trial tells us one specific pattern didn't beat another healthy-eating plan over three years. It doesn't tell us that what you eat is irrelevant.
Is all packaged food ultra-processed?
No. Tinned tomatoes, frozen peas, plain yoghurt, oats and tinned fish are packaged but lightly processed. A long ingredients list full of things you wouldn't find in a home kitchen is a reasonable clue that something is ultra-processed.
I have diabetes. What should I take from this?
That managing your blood sugar is worth it for more than one reason. Keep working with your GP or diabetes educator, especially if you take insulin or other glucose-lowering medicine.
About this article
Written by the I Quit Sugar team for the 8-Week Program, and reviewed against the peer-reviewed sources listed below.
Not medical advice. This article is general education. It isn't a diagnosis or a substitute for advice from your own health professional. If you're managing a medical condition, are pregnant or breastfeeding, or take medication, speak with your doctor before making significant changes to how you eat.
References
- Livingston G, Huntley J, Liu KY, et al. Dementia prevention, intervention, and care: 2024 report of the Lancet standing Commission. Lancet. 2024;404(10452):572–628. DOI
- Gudala K, Bansal D, Schifano F, Bhansali A. Diabetes mellitus and risk of dementia: a meta-analysis of prospective observational studies. J Diabetes Investig. 2013;4(6):640–50. DOI
- de la Monte SM. Type 3 diabetes is sporadic Alzheimer's disease: mini-review. Eur Neuropsychopharmacol. 2014;24(12):1954–60. DOI
- Morris MC, Tangney CC, Wang Y, et al. MIND diet slows cognitive decline with aging. Alzheimers Dement. 2015;11(9):1015–22. DOI
- Barnes LL, Dhana K, Liu X, et al. Trial of the MIND diet for prevention of cognitive decline in older persons. N Engl J Med. 2023;389(7):602–611. DOI
- Gomes Gonçalves N, Vidal Ferreira N, Khandpur N, et al. Association between consumption of ultraprocessed foods and cognitive decline. JAMA Neurol. 2023;80(2):142–150. DOI
- Cryan JF, O'Riordan KJ, Cowan CSM, et al. The microbiota-gut-brain axis. Physiol Rev. 2019;99(4):1877–2013. DOI
- Erickson KI, Voss MW, Prakash RS, et al. Exercise training increases size of hippocampus and improves memory. Proc Natl Acad Sci U S A. 2011;108(7):3017–22. DOI
- Ding D, Nguyen B, Nau T, et al. Daily steps and health outcomes in adults: a systematic review and dose-response meta-analysis. Lancet Public Health. 2025;10(8):e668–e681. DOI
- Greendale GA, Huang MH, Wight RG, et al. Effects of the menopause transition and hormone use on cognitive performance in midlife women. Neurology. 2009;72(21):1850–7. DOI
- Kravitz HM, Zhao X, Bromberger JT, et al. Sleep disturbance during the menopausal transition in a multi-ethnic community sample of women. Sleep. 2008;31(7):979–90. PubMed
