🧠 THE PERFORMANCE PULSE
This Week’s Newsletter – For Endurance Thinkers & High Performers
What’s Catching My Eye 👀
GLP-1s Are Starting to Reshape Supermarket Shelves
If you’ve walked through a supermarket recently, you may have noticed something subtle happening.
Smaller portion sizes.
Higher-protein ready meals.
Hydration products positioned around appetite suppression.
“Light”, “mini”, “controlled” packaging.
Retailers are beginning to respond to the rise in GLP-1 medications such as semaglutide and tirzepatide. As reported in The Grocer, the industry expects GLP-1 use to influence purchasing behaviour, meal frequency, snacking, and portion expectations.
From a commercial perspective, this is predictable.
From a clinical and performance perspective, it raises deeper questions.
If appetite is pharmacologically suppressed:
- Are people meeting protein needs?
- Are micronutrients being compromised?
- What happens to iron status, bone health, muscle mass?
- What happens to shared meals, social eating, cultural food traditions?
As someone involved in research and working directly with athletes wanting or even using these medications, I do wonder:
Are we at risk of creating a nation that is lighter… but potentially undernourished and at greater risk with lower muscle mass?
This space is evolving rapidly. And the food system is adapting before the long-term physiology is fully understood.
Watch this space.
Science Snapshot 🧬
Pre-Season Energy Deficiency Predicts Poorer Performance During a Competitive Season
https://onlinelibrary.wiley.com/doi/full/10.1002/ejsc.12261
With athletes preparing for major seasons right now with some already competing in Milan & Cortina, this study caught my attention.
🔬 What the study examined
The research investigated dietary intake and nutritional adequacy in competitive endurance runners during structured training periods. It assessed whether athletes were meeting energy and macronutrient requirements aligned with training demands.
🧪 Methods
- Competitive athletes (male and female)
- Observational dietary assessment study
- Food intake recorded and compared against established sport nutrition guidelines
- Energy availability and macro distribution analysed
📊 Key Findings
- Many athletes failed to meet recommended carbohydrate targets
- Some had inadequate energy intake relative to training load
- Protein intake was generally adequate, but distribution varied
- Risk of low energy availability was identified in subsets of athletes
🧠 What This Means
Even in structured environments like camps, with catering and professional oversight, athletes can unintentionally underfuel.
For endurance performance, this matters because:
- Low carbohydrate intake → reduced glycogen availability
- Low energy availability → impaired recovery, hormonal disruption
- Chronic underfueling → performance plateau and increased injury risk
⚖️ Study Quality
Strengths:
- Real-world athlete data
- Detailed intake analysis
- Direct relevance to applied sport nutrition
Limitations:
- Observational (not interventional)
- Short assessment period
- Self-reported intake limitations
Claire’s Takeaway Tip 🍽️
February Seasonal Veg – Don’t Waste It
February gives us:
- Swede
- Parsnips
- Leeks
- Carrots
- Cabbage
- Kale
- Beetroot
- Cauliflower
(Source: Love Food Hate Waste – https://www.lovefoodhatewaste.com/blog/whats-good-eat-month-february)
🥕 The Ultimate Leftover Root Veg Hash
Add beans or peas for extra fibre and plant protein.
Top with 1–2 eggs (>14g protein).
Add a side of Greek yoghurt or cottage cheese :
- Carbohydrates for glycogen
- 20g protein
- Fibre
- Micronutrients
- A brilliant post-training recovery meal
- Or a substantial endurance breakfast
This Week’s Deep Dive ➡️
“Diets Fail Because Advice Is Wrong,” Say Researchers
BBC Report: https://www.bbc.co.uk/news/health-14882832
The BBC recently revisited a longstanding issue in weight loss advice: the traditional “cut 500 kcal per day” rule. Researchers argue that this advice is overly simplistic and biologically misleading.
📉 Where Did the 500 kcal Rule Come From?
It stems from the old 3,500 kcal per pound rule, which assumed that a 3,500 kcal deficit equals 1 lb (0.45 kg) of fat loss.
However, modern research shows weight loss is dynamic, not linear.
- Hall et al., 2011 (The Lancet) demonstrated through metabolic modelling that energy balance adapts over time.
- Hall & Guo, 2017 (Obesity meta-analysis) showed the body resists weight loss through biological compensation.
- Egan & Collins, 2021 reviewed evidence confirming the 3,500 kcal rule overestimates real-world weight loss.
The body adjusts.
🔬 What Actually Happens During Weight Loss?
When calorie intake drops:
- Resting metabolic rate decreases
- Non-exercise activity reduces
- Adaptive thermogenesis occurs (energy expenditure falls beyond what weight loss alone explains)
- Lean mass is lost (~20–25% of weight loss; Heymsfield et al., 2014)
- Hunger hormones rise
This means the original 500 kcal deficit becomes smaller over time, leading to plateaus.
Large reviews (Stubbs et al., 2019; Turicchi et al., 2019) show that biological resistance mechanisms promote regain, especially after rapid or aggressive dieting.
🧠 What This Means
Weight loss is not a simple maths equation.
More so a biological adaptation.
Metabolism adapts.
So when diets fail, it is often not a willpower issue, it can be physiological.
For athletes and high performers, this matters even more. Chronic energy restriction can compromise:
- Lean mass
- Hormonal health
- Recovery
- Performance
Performance Pulse
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