Diet
This phrase is a bit ambiguous: it can mean way of eating, see below, or it can mean a temporary weight loss plan that you only do for a short amount of time, before returning to your previous diet. See? It's confusing!
WOE/Way of eating
The term diet has negative connotations, so many prefer WOE to indicate it's their plan to continue eating like this for the rest of their lives.
Calorie control/restriction/counting
A weight loss approach of writing down (paper or electronically) the calories of everything you eat and limiting that. This is the approach of the 12 week NHS plan.
Portion control
Calorie control's more louche sibling. Being mindful of how much you eat and limiting the portions, without the maths.
The Eat Well Guide
The official NHS/government advice in the UK on how to eat. It advises a WOE of over 80% total carbs (38% from starchy foods, and 40% of fruits and vegs, plus dairy), lean proteins and 1% added fats.
Low carb/low carb high fat/LCHF/keto/ketogenic
There are many WOEs that have less carbohydrates and more fat that the Eat Well Guide. It's a matter of opinion when reducing carbs becomes low carb. A lower or low carb WOE could reduce or eliminate some or all of: sugar, fruit, grains (eg bread, pasta, rice), starchy vegetables (eg potatoes)
Some take it much further, into ketogenic with as little as 20g of carbs per day, or even further to a carnivore WOE and virtually zero carbs.
Low Glycemic index/Glycemic load/GI/GL
This is a WOE that focuses on the type of carbs rather than quantity, choosing carbs that are slowly digested so not spiking blood glucose. It could be combined with increased fat and/or protein.
Calories in, calories out/CICO
If the amount of calories you ingest is greater than the amount your burn, you will gain weight; if it is less, you will lose weight. This principle is the foundation of calorie and portion controlled diets.
Intermittent fasting/Time restricted eating/IF/TRE
Some people consider when they eat as well as what they eat.
If this is done on a 24 hour cycle, it usually implies a fixed period of not eating each day (fasting) and a (usually shorter) eating window. Examples include 12:12 (ie not snacking between dinner and breakfast); 16:8 or 18:6 which could be 3 meals in 6 or 8 hours, but is often skipping breakfast or dinner entirely; one meal a day OMAD, also sometimes referred to as 23:1 or 24 hour fasting.
Some people fast or eat very little on some days and much more on others. That's usually described by number of days you fast, eg 5:2 (fasting 2 days each week), 4:3, alternative day fasting/ADF etc
Other useful acronyms
HM homemade
SW Slimming World
WW Weight Watchers
VLCD Very low calorie diet
DD Daily diary (a daily feature of our HU area)
BMI Body mass index
BMR Basal metabolic rate
C25K - couch to 5km, an NHS endorsed running training plan.
Notes:
* this is a complete rewrite, so some of the comments below refer to vastly different text.
* the purpose of this post is to answer the "what" questions. There are obviously "why" and "how" questions. Feel free to ask them below, or in new posts.