Never Make Important Decisions on an Empty Stomach (or Late in the Day)
by Dr. Delia McCabe, PhD

Our brain is our hungriest and most metabolically active organ. Although it only weighs between 1.3 to 1.4kg (2.9 – 3.1lbs) and accounts for 2% of our body weight, it uses 25%+ of our body’s energy consumption, depending on our age, energy demands, and stress, and uses 25% of the oxygen we breathe. 

The brain has nowhere to store energy, unlike the body, so a lack of fuel can directly impact attention, concentration, creativity, focus, learning, and mood.

Avoiding tigers, natural disasters, and foraging for food no longer demands our attention. Instead, lifestyle/work-related decisions, in an increasingly complex world, occupy our brains.
 

What is a decision?

A decision can be loosely defined as a neurological process that involves considering, judging and choosing between different options. We often think about making decisions as being linked to a purely cognitive, critical analysis of a situation, but our emotions are also linked to our decisions.

In fact, research has shown that when the parts of the brain involved in generating emotions become damaged, so too does decision-making. 

However, we also use the most sophisticated part of the brain, the prefrontal cortex (PFC), also called the CEO of the brain, to make decisions.

The PFC detects patterns in situations to predict outcomes, to ensure our survival. It assesses possible consequences and makes decisions that offer the best outcome based on patterns detected and previous experience (memory).

Consider the PFC to be the conductor of the brain - it facilitates emotional regulation, and supports optimal behavior and cognition. 

How many decisions do we make a day?

There is no supportive evidence for the commonly quoted number (35,000) of decisions we make per day. The only evidence we have available relates to daily decisions about food. 

Instead of making the estimated 14.4 decisions, participants in a study made an average of more than 221 food-related decisions per day. We obviously make many other, non-food decisions daily, however a more precise number of general decisions is not yet available. 

Regardless, neurological activity still underpins each decision and increases as options and responsibility increase.

Remember the story of prominent business figures who chose to wear the same type of clothes each day? They believed that decision fatigue sets in over a day of making decisions and wanted to save their cognition for important decisions. Were they right?

So, what is decision fatigue?

Researchers originally thought decision degradation occurred due to ‘using up’ our willpower, or self-control. They now believe that decision fatigue is the declining quality of decisions made after excessive decision-making. Several studies, including one around parole board judges’ decisions, report that as the day progresses, poorer decisions are made.

Early in the day, up to 70% of the prisoners received parole in the judge’s study, whereas later in the day this figure dropped to 10%. However, this tendency could be overcome if they took a small break to eat a meal. 

Using this logic, when we make fewer decisions overall, we limit the fatigue that plagues a brain over a day, which leaves more neural energy for important decisions. 

1) Brain energy and decision-making

Our brain's primary and preferred source of energy comes from carbohydrates, although the brain can use fat in the form of ketones as a source of energy when the carbohydrate supply runs low.

The PFC is extremely energy-demanding, using 25% of the total energy (20 – 25%) available to the brain. Fiber-filled, unprocessed carbohydrates provide a better source of brain fuel vs. processed food and support stable energy and blood glucose.

Several studies have revealed that blood glucose levels impact decision-making, with a recent meta-analysis summarizing the data: low levels of blood glucose increased the willingness to pay and work towards food-related situations but decreased the willingness to do either in non-food-related situations. In other words, low brain energy means less willingness to work towards non-food goals.

Low blood glucose also increased the tendency towards intuitive rather than deliberate decisions in situations unrelated to food.

So, people tend to make no decision when their brains are tired, or, revert to knee-jerk, habitual, decisions. 

2) Decision-making and stress 

Today we’re regularly faced with situations and thoughts that can induce stress. Although no tigers are hunting us, psychological stress elicits the same neurobiological response. 

This neurobiological response prompts a physical response that rushes glucose to our muscles to ‘fight or flee.’ Blood glucose quickly rises, then dips, which leads to compromised cognition. 

And, stress on its own, reduces the ability to make good decisions by virtue of the brain's preoccupation with survival vs. thriving when stressed. 

Some decisions induce stress too, which leads to a vicious cycle of increased stress and unbalanced blood glucose. 

So, blood glucose instability AND stress impact decision-making.

3) Blood glucose, stress and decision-making

Every decision we make uses neural energy. However, adrenalin, which is the currency of stress, also needs specific nutrients to be synthesized, many of which are the same nutrients required to synthesize neural energy. 

Survival is more important than lifestyle/work-related decision-making, so adrenalin synthesis takes precedence. Unfortunately, feeling stressed can also drive calorie-dense, nutrient-deficient, factory food consumption, in a desire to derive emotional comfort and increase energy, which further reduces the availability of nutrients to support optimal cognition. 

And a growing body of evidence links food choices and gut health to mental health. So, unstable blood glucose alone, combined with stress, and/or being tired, and reduced brain nutrient supply, combine to reduce optimal decision-making capacity. 

What to do? 

Use brain science to support optimal decision-making by ensuring your brain stays healthy:

1. Keep your blood glucose stable by choosing to eat foods rich in nutrients that support optimal energy synthesis and stable blood glucose and replace junk food with healthy, but delicious brain-supporting alternatives. 
2. Manage stress, using evidence-based mindfulness strategies, exercise, and sleep, all of which support stable blood glucose levels and improved decision-making.
3. Save neural energy by prioritizing important decision-making to early in the day vs. later in the day.
   
   

In conclusion, action evidence-based neuroscience to optimize decision-making.

References
Original article written by Dr. Delia McCabe, PhD, and authorized to be published in the World Management Agility Forum by Dr. Delia McCabe, PhD.