Welcome to this week’s deep dive into nutrition for high performers! Today, we’ll be discussing what foods we should consume to optimize our health, longevity, fat loss, and build lean muscle. With so many diets out there, it’s easy to get overwhelmed and confused, so we’re going to use a scientific lens to review the three main types of diets.
The Challenge: Too Much Conflicting Information
We all want to improve our health, build muscle, and shed excess fat, but when it comes to diet, the sheer number of options can leave you feeling lost. High-protein, low-carb? Plant-based? IIFYM (If It Fits Your Macros)? Each approach seems to have its advocates—and its skeptics.
Today, we’ll break these diets down into three general categories to give you a better understanding of what the science actually says.
IIFYM
You can eat whatever you want as long as your total macronutrients (protein, carbs, fat) are in line with your goals.
High Protein, Low Carb
Popularized by diets like the ketogenic and carnivore diets, where the focus is on protein as the primary macronutrient, with minimal carbs.
Plant-Based
Diets where most or all of your calories come from plant sources. This includes vegan and vegetarian diets with varying levels of restriction.
Let’s take a deeper look into these approaches and the research supporting or refuting their claims.
High Protein, Low Carb: Fat Loss and Satiety
A high-protein, low-carb approach has long been a favorite among athletes and fitness enthusiasts. The reasoning is simple: protein helps build muscle, keeps you full, and boosts fat burning.
One study, The Effects of High Protein Diets on Thermogenesis, Satiety, and Weight Loss, reviewed how high protein diets affect metabolism and hunger. It found that:
“Higher protein intake increases thermogenesis (fat burning) and satiety compared to diets with lower protein content. High protein meals also reduce subsequent energy intake, making it easier to avoid overeating.” (1)
What does this mean for you? A high protein diet can keep you feeling fuller for longer, helping you avoid overeating and promoting fat loss. But the benefits don’t stop there.
A second study, Clinical Evidence and Mechanisms of High-Protein Diet-Induced Weight Loss, concluded that high-protein diets are also great for preserving muscle while losing fat:
“Clinical trials show that consuming more protein than the recommended dietary allowance not only reduces body weight but also enhances body composition by decreasing fat mass while preserving fat-free mass.” (2)
So, if your goal is fat loss while maintaining lean muscle, a high-protein diet might be the way to go. Importantly, the study also found no adverse effects on bone density or kidney function, debunking a common myth about high-protein diets:
"Fairly long-term clinical trials of 6–12 months reported that a high-protein diet provides weight-loss effects and can prevent weight regain, without any adverse effects on bone density or renal function in healthy adults." (2)
The Ketogenic Diet: Great for the Short Term?
The ketogenic diet (KD), which emphasizes extremely low carbs and high fat intake, has shown impressive results, especially in the short term. According to a review titled Advantages and Disadvantages of the Ketogenic Diet:
“Within the first 6-12 months of initiating KD, transient decreases in blood pressure, triglycerides, and glycosylated hemoglobin, as well as increases in HDL cholesterol and weight loss, may be observed.” (3)
This makes keto diets appealing for those looking for rapid fat loss and quick improvements in metabolic health. However, the same review also highlights a key concern:
“These benefits are generally not seen after 12 months, as the changes reported in the studies reviewed were not statistically significant beyond the first year.” (3)
In other words, the ketogenic diet might provide excellent short-term results, but many people struggle to sustain the benefits long-term due to its highly restrictive nature.
Moreover, the challenge with high-protein, low-carb diets like keto and carnivore is their sustainability. Social events, travel, and even weekends can make it hard to stay 100% compliant with these diets. Research shows that long-term adherence is often low, leading to less consistent results.
Plant-Based Diets: A Mixed Bag
At the other end of the spectrum, plant-based diets have gained massive popularity due to their reported health benefits. Several studies support the idea that plant-based diets can reduce the risk of chronic diseases. For instance, one study on the health impact of vegan diets showed:
“A vegan diet decreases the risk of cardiometabolic diseases such as cardiovascular disease, type 2 diabetes mellitus, obesity, and non-alcoholic fatty liver disease.” (4)
However, plant-based diets also present some challenges. Research shows that vegans and vegetarians often struggle to get enough critical nutrients, including Vitamin B12, calcium, and Vitamin D. According to one study:
"Vegans consume insufficient calcium, Vitamin B12, and Vitamin D, which are crucial for bone and immune health.” (4)
Another study, Vegetarian and Vegan Diets and Risks of Total and Site-Specific Fractures, warns about the long-term risks:
"There was an increased risk of hip fractures among vegetarians compared to meat-eaters." (5)
In addition, Vitamin B12 deficiency in vegans may lead to serious health risks, including an increased risk of cancer, as noted in the research:
“B12 deficiency increases uracil misincorporation, impairing DNA synthesis and genomic instability, which may contribute to carcinogenesis.” (6)
While plant-based diets offer many benefits, they also require careful planning to avoid nutrient deficiencies and potential long-term risks.
IIFYM: Flexibility with Trade-offs
IIFYM (If It Fits Your Macros) is a flexible dieting approach where you can eat anything as long as it meets your macronutrient goals. While there isn’t as much formal research on IIFYM, it’s widely accepted that this approach can work for building muscle, losing fat, or weight management.
However, the downside is that IIFYM can promote unhealthy eating habits. For example, you might be able to fit a McDonald’s Big Mac into your daily calorie intake, but you’d likely be hungry all day due to the calorie-dense, nutrient-poor nature of processed food.
Highly processed and sugary foods can leave you unsatisfied and craving more, making it harder to stick to your goals. In short, IIFYM can work for body composition, but it may not be optimal for overall health.
What’s the Optimal Diet?
After reviewing the science behind each approach, it’s clear that there are benefits and drawbacks to each diet. So, what’s the best approach for high performers looking to optimize health, longevity, fat loss, and lean muscle?
The Winning Formula:
Focus on High-Quality Protein. Lean meats, fish, eggs, and dairy are essential for building muscle, staying full, and losing fat.
Plenty of Fruits and Vegetables. These provide fibre for gut health, keep you full, and deliver essential vitamins and minerals.
Healthy Fats and Whole-Carb Sources. Include healthy fats like olive oil, avocado, and nuts, along with complex carbs like sweet potatoes and whole grains to fuel your workouts.
Flexibility for Sustainability. Allow for some flexibility in your diet. If it’s your birthday, have a slice of cake. If you’re on vacation, enjoy the local cuisine. Just make sure that 90% of your diet is made up of whole, nutrient-dense foods.
Sample Day of Eating for High Performers
Morning:
500ml warm water with lemon, creatine, Vitamin D, Omega 3
3 whole eggs, spinach and pepper omelette, 10 almonds, 1 carrot, 25ml pure cranberry juice
Mid-Morning:
1 liter ginger and lemongrass tea
Lunch:
1 tin of tuna, sweet potato mash or new potatoes, raw veggies (cucumber, carrot, celery), dressed with olive oil, salt, and lemon
Afternoon:
500ml water
Main Training: 500ml water
Dinner:
4-8 oz rump steak, ½- 1 cup of rice, spinach, 200ml chicken bone broth
Evening Snack:
½- 1 cup full-fat Greek yogurt with berries
Takeaways:
Protein is King – Aim for 1g of protein per lb of body weight for muscle building and fat loss.
Fibre is Key – Load up on fruits and veggies for gut health, digestion, and satiety.
Be Flexible – Allow yourself indulgences occasionally, but get back on track at your next meal.
References
Halton TL, Hu FB. The effects of high protein diets on thermogenesis, satiety, and weight loss: A critical review. J Am Coll Nutr. 2004.
Moon J, Koh G. Clinical Evidence and Mechanisms of High-Protein Diet-Induced Weight Loss. J Obes Metab Syndr. 2020.
Batch JT, et al. Advantages and Disadvantages of the Ketgenic Diet: A Review Article. Cureus. 2020 Aug 10;12(8):e9639. doi: 10.7759/cureus.9639. PMID: 32923239; PMCID: PMC7480775.
Bali A, Naik R. The Impact of a Vegan Diet on Many Aspects of Health: The Overlooked Side of Veganism. Cureus. 2023 Feb 18;15(2):e35148. doi: 10.7759/cureus.35148. PMID: 36950003; PMCID: PMC10027313.
Tong TYN, Appleby PN, Armstrong MEG, Fensom GK, Knuppel A, Papier K, Perez-Cornago A, Travis RC, Key TJ. Vegetarian and vegan diets and risks of total and site-specific fractures: results from the prospective EPIC-Oxford study. BMC Med. 2020 Nov 23;18(1):353. doi: 10.1186/s12916-020-01815-3. PMID: 33222682; PMCID: PMC7682057.
Loedin AK, Speijer D. Is There a Carcinogenic Risk Attached to Vitamin B12 Deficient Diets and What Should We Do About It? Reviewing the Facts. Mol Nutr Food Res. 2021 Mar;65(6):e2000945. doi: 10.1002/mnfr.202000945. Epub 2021 Feb 19. PMID: 33548097; PMCID: PMC8126961.
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