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How to Eat After 40: The Nutrition Targets That Matter Most

October 18, 2026

I don’t know about you, but I could get away with eating just about anything in my 20s and 30s. 

But the older I got, the less true that became—and the more my dietary habits started catching up with me. 

If you’re nearing or past midlife, you’ve probably noticed something similar.

That occasional 11 p.m. slice of pizza, once no biggie, now leads to hours of tossing and turning. Certain breakfast foods—bagels, donuts, croissants—trigger a midmorning energy crash. And that glass of red wine at dinner comes with a throbbing headache the next morning. 

There’s a reason for that. 

As you move through your 40s, 50s, and beyond, changes in your muscles, hormones, digestion, and metabolism can shift how your body processes food. 

Yet the mistake many people make is assuming their diet doesn’t need to evolve as they do.

Here are the five daily nutrition targets to prioritize after 40—plus how to identify gaps and personalize your diet as your body continues to change.

How Age Impacts Your Dietary Needs 

Around middle age, your body changes in several ways that impact the right diet for you.

▶ Stomach acid production declines—a problem that can be worsened by acid-lowering heartburn medications. This can slow digestion, reduce protein breakdown, and make it harder to absorb nutrients such as vitamin B12, calcium, iron, and magnesium.^1,2 As a result, large meals may leave you feeling bloated or overly full, and some people may need extra support to meet their nutrient needs.

▶ Digestion slows. As you age, you may have lower levels of digestive enzymes and weaker intestinal muscles, which may lead to gas, bloating, and constipation. Eating enough fiber and staying hydrated become even more critical.³

▶ Muscle and bone become harder to build and maintain. To compensate, you’ll need more protein when you’re 40 and beyond than you did when you were 20 or 30. You may also need additional supplements to support bone and muscle mass.⁴

▶ Cells become insulin resistant. You may find that eating high-starch, high-sugar foods leaves you feeling wiped out, foggy, and irritable thanks to the blood sugar rollercoaster. Even high amounts of otherwise nutritious foods such as beans and fruit can be problematic for some people after middle age, especially if they’re sedentary.⁵

▶ Calorie needs may decrease. Many people move less as they get older, and thus need fewer calories. Metabolism can also slow, especially if muscles atrophy. You’ll likely need to eat less to fend off weight gain—but the nutrient content of the foods you do eat becomes even more important. 

How to Eat for Your Age

Whether you’re in your 20s, 40s, 60s, or 80s, the fundamental nutrition principles remain largely the same. Everyone should be eating real, minimally processed, nutrient-dense whole foods most of the time. 

What changes as you age is this: How closely you need to follow the fundamentals.

If you’re in your 20s, you likely have more wiggle room. If you mostly eat health-promoting foods—say, 60% or 70% of the time—you might be able to indulge the rest of the time and still feel great. 

However, if you’re in your 40s or beyond, you’ll likely find that you need to put more emphasis on loading your plate with protein, veggies, and other health-promoting foods far more of the time to avoid issues like low energy, digestive discomfort, muscle and bone loss, and nutrient deficiencies. 

And the older you get, the closer you’ll need to stick to the plan. 

Use the following four strategies to get the balance just right.

Strategy #1: Start Hitting These 5 Nutrition Targets

Make sure you check everything off the list every single day:  

1. Eat 12–18 servings of vegetables. (Check out this meal-by-meal guide and helpful tips.) 
   
   
2. Eat 1.2–1.6 grams of protein per kilogram of body weight. For example, if your target weight is 150 pounds, you would aim for roughly 82–109 grams per day. (Learn how to double your protein intake.)
   
   
3. Drink half your body weight in ounces of water. For example, if you weigh 150 pounds, drink 75 ounces. 
   
   
4. Eat a source of healthy fat at every meal—and low-mercury, omega-3-rich fatty fish at least three times a week. 
   
   
5. Eat 30+ grams of fiber. (Here are three useful fiber strategies if you need some help.) 

This might require more intentional planning as you get older. For example, thirst and hunger cues can change. So, keep your eye on the target.  

You can also make a game out of choosing the healthiest, most nutrition-packed version of each food you eat to hit these goals. For example, if you choose wild blueberries over cultivated ones, you’ll net more health-promoting antioxidants.⁶ And unfiltered extra virgin olive oil offers more health-promoting polyphenols than filtered and light olive oils.⁷ These positive choices compound over time. 

Strategy #2: Patch Common Deficiencies 

Even if you consumed the most health-promoting foods 100% of the time, you’d likely still fall short on your intake of several key nutrients thanks to those age-related changes in digestion. 

You can find out exactly where you might have gaps by getting your labs done with Function Health. (Use code MARK2026 to unlock a $50 credit.) Once you have your results, you can determine where you need additional support. 

For most of my patients over 40, I often recommend the following five foundational supplements as “nutritional insurance:”   

• A high-quality multivitamin and mineral supplement, such O.N.E. Multivitamin by Pure Encapsulations
  
  
• Vitamin D3, such as Vitamin D3 by Pure Encapsulations 
  
  
• Omega-3 fatty acids (EPA/DHA), such as Omega-3 Rejuvenate by Big Bold Health 
  
  
• Magnesium glycinate (gentle on the stomach) or magnesium citrate (good for constipation), or a combined product such as Magnesium Breakthrough by Bioptimizers  
  
  
• A probiotic or synbiotic, such as Seed DS-01® Daily Synbiotic 

Always talk with your healthcare provider before adding any new supplement, especially if you take medications or have existing health conditions. 

Strategy #3: Experiment with a Continuous Glucose Monitor 

How well you control blood sugar is an important marker of metabolic health as you age. Insulin resistance and chronically elevated blood sugar are linked with a higher risk of many age-related conditions, including type 2 diabetes, heart disease, dementia, and some cancers.⁸

Understanding how your blood sugar responds to different foods can help you personalize your diet—and a continuous glucose monitor (CGM) can show you what’s happening in real time. 

If you’re insulin resistant, you may need to be more mindful of portions of carbohydrate-rich foods—even nutritious ones such as beans, whole grains, root vegetables, and fruit. If you’re metabolically healthy and physically active, you may tolerate those same foods much better. 

The CGM provides clear data that can help you make informed dietary decisions going forward. You can also retest every year or two to see if things need to shift as your body changes over time.  

Strategy #4: Consider a Regular Reset

My 10-Day Detox eliminates the foods most likely to lead to GI upset, fatigue, headaches, and other woes in people aged 40 and beyond—and adds an abundance of whole, minimally processed foods full of health-boosting fiber and nutrients. 

Many of my patients do the Detox every 6–12 months as a dietary reset that reminds them just how good they can feel. It’s also a fantastic way to get back on track with your nutrition fundamentals if things have slipped over time—and all you need is 10 days. Learn more about my 10-Day Detox.

References

1. Hinssen F, Mensink M, Huppertz T, van der Wielen N. Impact of aging on the digestive system related to protein digestion in vivo. Crit Rev Food Sci Nutr. 2025;65(28):5871–87.

2. Beaudry-Richard A, Abdelhak A, Saloner R, Sacco S, Montes SC, Oertel FC, et al. Vitamin B12 levels association with functional and structural biomarkers of central nervous system injury in older adults. Ann Neurol. 2025 June;97(6):1190–204.

3. Zhang P, Wu P, Li C, Deng R, Chen XD. Modeling age-related gastrointestinal changes in food digestion: progress and challenges in transitioning from in vivo studies to physiologically relevant in vitro systems. Curr Opin Food Sci. 2025 Dec;66(101357):101357.

4. Pérez-Castillo ÍM, Rueda R, Pereira SL, Bouzamondo H, López-Chicharro J, Segura-Ortiz F, et al. Age-related anabolic resistance: Nutritional and exercise strategies, and potential relevance to life-long exercisers. Nutrients. 2025 Nov 9;17(22):3503.

5. Huang LY, Liu CH, Chen FY, Kuo CH, Pitrone P, Liu JS. Aging affects insulin resistance, insulin secretion, and glucose effectiveness in subjects with normal blood glucose and body weight. Diagnostics (Basel). 2023 June 24;13(13):2158.

6. Liu RH. Dietary bioactive compounds and their health implications. J Food Sci. 2013 June;78 Suppl 1(s1):A18–25.

7. Gorzynik-Debicka M, Przychodzen P, Cappello F, Kuban-Jankowska A, Marino Gammazza A, Knap N, et al. Potential health benefits of Olive oil and plant polyphenols. Int J Mol Sci. 2018 Feb 28;19(3):E686.

8. Kurauti MA, Soares GM, Marmentini C, Bronczek GA, Branco RCS, Boschero AC. Insulin and aging. Litwack G, editor. Vitam Horm. 2021 Feb 1;115:185–219.