Hard-working muscles run primarily on glycogen, a form of carbohydrate stored in our liver and muscle. Carbohydrates, which come almost exclusively from plants, also provide our brain with its primary and preferred fuel — glucose — which helps us stay sharp and focused during intense training sessions and competitions .

Performance-based diets built around meat and other animal products often provide dietary fat at the expense of carbohydrates. Unlike carbohydrates, fat can’t produce energy fast enough to meet the demands of intense exercise, so diets that sacrifice carbohydrates typically impair high-intensity performance. Low-carbohydrate diets, including the ketogenic (keto) diet, have been shown to cause so much fatigue that they even affect our motivation to begin a training session, let alone finish it.

Protein can also be used as a fuel source, but it’s highly inefficient, wasting 20-30% of each calorie as heat (9).

All told, carbohydrates are the ideal source of energy for optimized performance, whether it’s doing squats, playing football, or running a marathon.

And as we’ll discuss later in Getting and Staying Lean, despite the common misconception that “carbs make you fat”, unrefined carbohydrates — like those found in whole plant foods, including oats, sweet potatoes, and bananas — are consistently associated with decreased body fat, another advantage for most performance goals.

animal-based meals can cripple our arteries, preventing them from fully opening to allow for increased blood flow. Research has shown that just two hours after eating a heavy animal-based meal, arteries can constrict by 40%, essentially causing a traffic jam. The calorie-matched plant-based meal allowed them to open freely for quick, easy transit.

But it isn’t just the lack of “baggage” in plant foods that help keep our blood flowing quickly; there is also a common ingredient found in plant-based foods like spinach, lettuce, carrots, and beets that actually signals our blood vessels to open, allowing more blood to flow through at a faster pace. This ingredient is nitrates which, unlike the cancer-causing nitrates in cured meats like bacon, serves another important function.

 

REDUCED INFLAMMATION

Inflammation is our bodies’ natural immune response to injury, foreign invaders, or even exercise. In its acute form, like after spraining an ankle, coming down with a bacterial infection, or recovering from a workout, inflammation is an immediate and necessary part of the healing process. Left unchecked, or further intensified, inflammation can prolong healing time from injuries or sickness, and also increase soreness and swelling, slowing recovery between workouts and competitions.

Chronic inflammation often begins with the same cellular response, but shifts in nature when the immune system fails to heal the injury effectively, eliminate the foreign invaders, or continues to respond to a threat that no longer exists. Once it reaches this stage, inflammation often begins damaging healthy tissues, including muscles and joints.

Taking all of this into account, unnecessary inflammation can have a significant negative impact on our physical performance ().

Fortunately, diet can be a powerful tool to get us through acute inflammation faster and combat chronic inflammation as well. But it can also have the opposite effect.

Animal-based diets fall into the latter category. Extensive research has shown that meat and other animal products contain (or lead to the formation of) a wide range of pro-inflammatory compounds and molecules, including bacterial endotoxins, trimethylamine N-oxide (TMAO), nitrosamines, heterocyclic amines (HCAs), N-Glycolylneuraminic acid (Neu5Gc), and polycyclic aromatic hydrocarbons (PAHs). If these words sound scary, you’re right: the damage they inflict can be severe, with research showing that a single hamburger can increase measures of inflammation by 70 percent.

Plants fall on the opposite end of this spectrum, coming naturally packed with high doses of anti-inflammatory compounds, including thousands of powerful antioxidants. The contrast between these two classes of food is dramatic, with plants having on average 64 times the antioxidant content of animal foods. This helps explain why switching to a plant-based diet can help reduce measures of inflammation by 29 percent in just three weeks (28).