How to optimize nutrition for athletic performance and recovery

Originally published on December 1, 2025

How to optimize nutrition for athletic performance starts with a practical question: are you actually fueled when your body needs fuel most? Registered sports dietitian Angie Asche explains why stable body weight can still hide underfueling, why low-carb and low-fat habits often backfire, and how better meal timing can improve energy, sleep, and recovery.

In Episode 351 of the WHOOP Podcast, Asche joins Dr. Kristen Holmes, Global Head of Human Performance, Principal Scientist at WHOOP, to break down what she sees with athletes in Major League Baseball and the National Hockey League, along with high-stress executives. The conversation turns a complicated topic into clear decisions people can use right away.

To listen to Episode 351 of the WHOOP Podcast in full, head to the WHOOP Podcast on YouTube.

Originally published on December 1, 2025

What does underfueling actually look like when body weight is stable?

Underfueling can show up through timing as much as through total calories. A person can maintain weight, or even gain weight, and still start training sessions, practices, or games without enough available energy.

That distinction matters in performance settings because the body needs fuel before, during, and after work, not only by the end of the day. Asche points out that athletes often assume underfueling only counts when weight is dropping. In practice, she sees a different pattern: long stretches without food, a light intake before training, and then a large intake after the hardest work is already over. That pattern can still fit the broader picture of low energy availability, the issue addressed in the Relative Energy Deficiency in Sport consensus.

Asche says the first step is to look at when energy is arriving, not only how much arrives over 24 hours. An athlete who skips breakfast, relies on coffee through midday, trains hard, and then eats most of the day’s calories late at night may hit a calorie target while still missing the moment when performance needed fuel most.

In the conversation, Asche gives a definition that is unusually clear and useful for coaches, athletes, and anyone training hard:

“Technically, even if you’re maintaining your weight or even if you’re gaining weight, you can actually still be underfueled. And it’s really just a matter of that nutrient timing and not fueling your body in key moments when it needs it most.”

That framework also helps explain why underfueling is easy to miss. It may not announce itself on a scale. It often shows up first as flat practices, slower recovery, poor concentration, or a session that feels much harder than it should.

What you should take away

• Underfueling can happen even when body weight stays stable or trends up.
• Meal timing affects performance because the body needs energy when training stress is happening, not only after it is over.
• Long gaps without food can reduce available energy even if total daily intake looks acceptable on paper.
• Stable weight does not rule out low energy availability.

If you want to hear Asche unpack how underfueling can hide behind stable body weight, listen to the full episode on Youtube.

Why does chasing leanness often hurt performance?

Chasing a leaner look often pushes athletes to cut the very nutrients that help them train, recover, and stay healthy. In Asche’s experience, the most common cuts are carbohydrates and fats, while protein usually stays high.

That pattern came up in stories she shared about a hockey player and a pitcher whose main goal was getting under 10 percent body fat. The goal was aesthetic, not performance driven. Both athletes felt worse through the season, and both dealt with injuries. Asche’s point was simple: the body reads chronic restriction as a shortage, even when the plan looks disciplined from the outside.

Women can show the cost of restriction faster because menstrual function gives a visible signal. Men often stay in the same cycle longer before anyone connects the fatigue, low mood, or poor recovery to nutrition. Asche said that difference can make people think underfueling is mainly a women’s issue, when the problem is common across both sexes.

Fat intake deserves special attention here. Earlier in the conversation, Asche noted that dropping fat below about 20 percent of total calories can start to affect hormonal health. For endurance athletes, and especially for women, she sees low fat intake often overlooked because so much attention goes to carbohydrate intake around sessions.

Those mindsets can take years to unwind, especially in sports where appearance and body composition are always visible. WHOOP members who want more context on how restrictive thinking affects performance can also read Eating Disorders and Their Impact on Performance, which explores the long tail of food rules and body image pressure.

Asche described the cycle with an example that gets to the heart of the issue:

“Their main goal was to just get leaner. They just wanted to get under that 10%. They really want to be under 10%. And there really wasn’t a reason why. It was just more aesthetic.”

When the goal shifts from looking leaner to performing better, nutrition decisions tend to improve. Athletes start eating for output, not only appearance, and that usually means restoring the carbohydrates and fats that restriction removed first.

What you should take away

• A leaner look does not guarantee better performance, better recovery, or lower injury risk.
• Carbohydrates and fats are the macronutrients athletes most often cut when they chase body fat targets.
• Women may show the effects of underfueling sooner through menstrual changes, while men can miss the pattern for longer.
• Fat intake that stays too low can affect hormonal health, especially in endurance athletes.

If you want to hear Asche go deeper on the tension between aesthetics and performance, listen to the full episode on Youtube.

How should athletes time carbohydrates, protein, and fats across the day?

Athletes generally do better when carbohydrates and protein are distributed around training instead of packed into a short eating window. Asche’s advice is practical: get the right nutrients in before, during, and after work, then use the rest of the day to support total intake.

That is where intermittent fasting gets complicated. Asche said she has seen fasting help some male executives who benefit from stricter boundaries around late-night eating. Athletes are different. A baseball player trying to reach 4,800 calories in a day has a much harder job if eating does not start until noon and stops at 8 p.m., especially when the game starts at 7 p.m. and postgame recovery still needs food.

She also pushes back on the idea that every athlete needs a big breakfast. Her focus is more precise than that. The first goal is to stop entering work underfueled. For some people that means breakfast. For others it may mean a smaller early feeding plus a stronger pre-workout and during-workout plan. What matters is that the body has carbohydrate available for training and protein available for repair.

This section of the conversation lines up with broader WHOOP Locker guidance on nutrition habits and meal timing, where the same pattern shows up again: consistency around meals often supports recovery better than large swings in intake.

Asche boiled her approach down to one concrete rule:

“Let’s try to at least get some of the right nutrients, and by the right nutrients, carbohydrates, protein, pre, during, and post. If we can at least get the timing spot on with that, then you’ll see a world of a difference with performance, with recovery, with sleep, all of it.”

That advice is also why she is cautious about fasting for athletes. The tighter the eating window, the easier it becomes to miss pre-session fuel, post-session recovery, or both.

What you should take away

• Nutrient timing can improve performance even when total daily calories stay the same.
• Carbohydrates and protein deserve priority before, during, and after training sessions.
• Intermittent fasting can make it harder for athletes to meet energy needs, especially in sports with evening competition.
• A good fueling plan is built around training demands, not around rigid meal timing rules.

If you want to hear Asche unpack fasting, calorie distribution, and pre and post training fuel, listen to the full episode on Youtube.

How can underfueling change sleep, recovery, and perceived effort?

Underfueling can make training feel harder, increase irritability, and disrupt sleep. Asche connects those effects to both physiology and daily routine.

She explained that chronic underfueling can lower leptin and raise cortisol later in the day, which makes it harder to settle into sleep. In practical terms, the athlete feels wired at night and flat the next day. The cycle can then feed itself. Poor sleep dampens appetite early in the day, intake stays low again, caffeine use rises, and late-night hunger grows.

Asche used baseball to show how this unfolds. Some players go all morning without eating, take in coffee instead of food, have a light pregame meal because they do not like playing on a full stomach, eat very little carbohydrate during the game, and then do most of their damage on snacks and high-fat foods after midnight. They may finally eat a lot, but the timing works against sleep and recovery.

That is one place where WHOOP data can be useful. When late-day underfueling turns into late-night overeating, people may see a pattern of worse Sleep, lower Recovery, and a higher resting heart rate across a series of hard days. The device cannot tell you what to eat, but it can show whether the routine around food is supporting the way you want to feel and perform.

Asche described the mechanism directly:

“We see an increase in cortisol when athletes are chronically underfueled. So they are in a chronic energy deficit. We see that increase in cortisol in the evening, essentially.”

She also noted the subjective signs that usually show up first: higher rate of perceived exertion, persistent fatigue, brain fog, mood swings, and trouble staying focused. When the same workout suddenly feels harder, nutrition deserves a look before you assume the plan itself has failed.

What you should take away

• Chronic underfueling can affect sleep by shifting hunger hormones and evening cortisol in the wrong direction.
• Higher perceived exertion is a common sign that energy availability is too low.
• Late-night overeating often grows out of poor intake earlier in the day.
• WHOOP trends can help show whether a fueling routine is supporting sleep and next-day recovery.

If you want to hear Asche go deeper on sleep disruption, late eating, and harder-feeling workouts, [watch the full episode on YouTube]([Link needed once live])

Are gut tests, food sensitivity tests, and supplements worth it?

Some are useful, but Asche is skeptical of the most heavily marketed tests. Her standard is straightforward: if a test mostly leads back to basic diet advice, it may be adding cost and confusion more than value.

On microbiome and stool mapping tests, Asche said the common output is generic advice to eat more prebiotic fiber and consider a probiotic. She would rather start with diet history, symptom patterns, training load, how often someone gets sick, and basic bloodwork that might reveal unexplained deficiencies. For the at-home IgG food sensitivity tests, her criticism was stronger. She said they often flag foods eaten recently, which can create false positives and unnecessary fear around nutrient-dense staples.

That concern matters because false certainty can narrow a diet quickly. An athlete who starts avoiding foods based on a weak test may lose variety, fiber, and total energy intake at the same time. A better sequence is to look at symptoms, talk with a qualified clinician, and use targeted testing when the question is clear.

Asche also gave practical supplement guidance. She prefers food first for probiotics, using yogurt and kefir as examples that bring protein and minerals along with live cultures. For omega-3s, she often recommends about 2 grams per day when fish intake is low. She said a rough food benchmark is two 4 ounce salmon servings per week. If a supplement is needed, take it with a meal that includes fat. She estimated that about 10 grams of fat in the meal helps absorption. On minerals, she noted that calcium and iron can compete for absorption, coffee can reduce iron absorption, and vitamin C can help it.

The same food-first logic shows up in other WHOOP nutrition conversations, including Food as Medicine with Dr. Julie Foucher, where diet quality matters more than supplement stacks built on guesswork.

Asche summed up her concern about trendy testing in one line:

“The marketing has just been far, far, far quicker than any of our research.”

That is a useful filter well beyond gut testing. If a product promises precision but keeps sending people back to the same basics, the basics still deserve first priority.

What you should take away

• Microbiome and stool tests often lead to broad advice that can be reached from diet history and symptom review.
• At-home IgG food sensitivity tests can create false positives and unnecessary food fear.
• Probiotic foods such as yogurt and kefir often make more sense than defaulting to a supplement.
• Omega-3 supplements are most useful when fish intake is low, and they should be taken with a meal that contains fat.

What supports long-term metabolic health and better fueling for women?

Long-term metabolic health starts with repeatable basics: daily movement, resistance training, enough fiber, and enough total fuel. Asche argues that these habits support short-term performance and long-range health at the same time.

She is especially direct about movement and muscle. Walking counts. Lifting matters. Muscle acts like a glucose sponge, which is one reason resistance training supports better glucose handling across the lifespan. That point becomes even more urgent for women moving into perimenopause and menopause, when insulin resistance can rise and estrogen declines can change body composition and recovery.

Food quality still matters inside that bigger picture. Asche challenged the excuse that there is no time to cook by asking people to compare meal prep time with screen time. Her suggestion was simple: cut social media time in half and use part of that saved time to wash berries, chop vegetables, prep grains, or build ready-to-go snacks such as Greek yogurt bowls with seeds and fruit.

Fiber sits at the center of this section. Asche said the average American gets only about 10 to 15 grams per day, while general targets are at least 25 grams for women and up to 38 grams for men. Whole-food sources remain her preference, and she also mentioned psyllium husk as a useful add-on for people trying to increase fiber and support LDL cholesterol.

Women who want a deeper follow-on read can pair this episode with Science-Backed Nutrition Tips for Women with Dr. Hazel Wallace. For the muscle side of the equation, Protein and Skeletal Muscle: The Keys to Longevity with Dr. Gabrielle Lyon adds more detail on why preserving lean mass matters over time.

Asche gave one of the clearest numbers in the episode when she turned to fiber:

“I want to say the average American gets 10 to 15 grams a day when they should be getting at least 25, if not up to like 38 grams for men daily.”

Her broader message for women was equally clear. Eating more to support training is different from eating more to chase size. Better fueling, especially enough carbohydrates and fats, helps performance, recovery, hormonal health, and long-term metabolic function.

What you should take away

• Daily walking and resistance training support both short-term performance and long-term metabolic health.
• Fiber intake remains low for many adults, and whole-food sources are the best place to start.
• Women, especially endurance athletes, often under-eat fat while trying to support training.
• A few minutes of meal prep can improve diet quality far more than another stretch of social media scrolling.

The bottom line

• Underfueling can exist even when body weight is stable, because nutrient timing affects whether energy is available when training demands it.
• Chasing a lower body fat percentage often leads athletes to cut carbohydrates and fats first, which can reduce performance and raise recovery problems.
• Pre, during, and post training fueling with carbohydrates and protein is one of the fastest ways to improve energy, sleep, and repeatability across hard sessions.
• Chronic underfueling can push evening cortisol higher, which can make sleep harder and leave the next day’s workout feeling harder than expected.
• Late-night overeating often starts with poor intake earlier in the day, especially when coffee replaces meals and pregame meals stay too light.
• Microbiome mapping and at-home IgG food sensitivity tests often add less value than careful review of symptoms, food intake, bloodwork, and training load.
• Long-term metabolic health is supported by repeatable basics, especially walking, resistance training, enough fiber, and enough total fuel.
• Women who train hard often need more support around adequate fat intake, hormonal health, and the mindset shift from eating less to fueling better.

Frequently asked questions about things discussed in this episode

How does WHOOP help you spot signs of underfueling?

WHOOP can help you spot a possible underfueling pattern by showing repeated combinations of lower Recovery, worse Sleep, and a higher resting heart rate after hard training blocks. Those trends do not diagnose low energy availability on their own, but they can show when meal timing and total intake deserve a closer look.

What does WHOOP show when late eating is affecting sleep?

WHOOP can show the downstream pattern of late eating through weaker Sleep results and poorer next-day Recovery. The signal is most useful when the same pattern repeats across several nights instead of being judged from one late meal.

How does WHOOP help you evaluate fasted training?

WHOOP helps you evaluate fasted training by showing whether the practice lines up with stable sleep and recovery or with a drop in both. If fasted sessions repeatedly lead to worse bounce-back, the tradeoff is probably too costly for your current training load.

What does WHOOP do for tracking nutrition changes across a week?

WHOOP makes weekly pattern review easier because nutrition effects often show up across several days rather than in one isolated session. That is useful when you are adjusting meal timing, post-workout fueling, fiber intake, or caffeine habits.

How can WHOOP support women who are trying to fuel better for training?

WHOOP can support better fueling decisions by showing whether higher intake around training lines up with steadier Recovery and better Sleep. That trend view can be especially helpful when a woman is trying to separate fear of eating more from the real goal of supporting performance.

What does WHOOP help you learn about pre and post workout fueling?

WHOOP helps you connect pre and post workout fueling to outcomes you can actually track, including sleep quality, recovery trends, and how repeatable hard sessions feel across a week. Used consistently, that makes meal timing easier to judge against training demands.

Used alongside smarter meal timing and enough daily fuel, WHOOP can help you see whether your nutrition plan is actually supporting the sleep and recovery your training requires.